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MEDARM: A rehabilitation robot with 5DOF at the shoulder complex

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Abstract and Figures

A key approach for reducing motor impairment and regaining independence after stroke is frequent and repetitive functional training. A number of robotic devices have been developed to assist therapists with the labourious task of providing treatment. Although robotic technology is showing significant potential, its effectiveness for upper limb rehabilitation is limited in part by the inability to make functional reaching movements. A major contributor to this problem is that current robots do not replicate motion of the shoulder girdle despite the fact that the shoulder girdle plays a critical role in stabilizing and orienting the upper limb during activities of daily living. To address this issue, a new adjustable robotic exoskeleton called MEDARM is proposed for motor rehabilitation of the shoulder complex. MEDARM provides independent control of six degrees of freedom (DOF) of the upper limb: two at the sternoclavicular joint, three at the glenohumeral joint and one at the elbow. Its joint axes are optimally arranged to mimic the natural upper- limb workspace while avoiding singular configurations and while maximizing manipulability. This mechanism also permits reduction to planar shoulder/elbow motion in any plane by locking all but the last two joints. Electric motors actuate the joint using a combination of cable and belt transmissions designed to maximize the power-to-weight ratio of the robot while maintaining backdriveability and minimizing inertia. Thus, the robot can provide any level of movement assistance and gravity compensation. This paper describes the proposed technical design for MEDARM.
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MEDARM: a rehabilitation robot with 5DOF at the shoulder complex
Stephen J. Ball, Ian E. Brown and Stephen H. Scott
Abstract A key approach for reducing motor impairment
and regaining independence after stroke is frequent and
repetitive functional training. A number of robotic devices
have been developed to assist therapists with the labourious
task of providing treatment. Although robotic technology is
showing significant potential, its effectiveness for upper limb
rehabilitation is limited in part by the inability to make
functional reaching movements. A major contributor to this
problem is that current robots do not replicate motion of
the shoulder girdle despite the fact that the shoulder girdle
plays a critical role in stabilizing and orienting the upper limb
during activities of daily living. To address this issue, a new
adjustable robotic exoskeleton called MEDARM is proposed
for motor rehabilitation of the shoulder complex. MEDARM
provides independent control of six degrees of freedom (DOF)
of the upper limb: two at the sternoclavicular joint, three
at the glenohumeral joint and one at the elbow. Its joint
axes are optimally arranged to mimic the natural upper-
limb workspace while avoiding singular configurations and
while maximizing manipulability. This mechanism also permits
reduction to planar shoulder/elbow motion in any plane by
locking all but the last two joints. Electric motors actuate
the joint using a combination of cable and belt transmissions
designed to maximize the power-to-weight ratio of the robot
while maintaining backdriveability and minimizing inertia.
Thus, the robot can provide any level of movement assistance
and gravity compensation. This paper describes the proposed
technical design for MEDARM.
Index Terms rehabilitation, robot, shoulder girdle, stroke
TROKE is a leading cause of disability in Canada,
leaving people with motor deficits that limit their ability
to perform activities of daily living. Impairments may involve
loss of a combination of motor, sensory and/or cognitive
functions including weakness, reduced coordination, dimin-
ished ability to think, communicate, and make decisions, as
well as to feel, see and hear. Currently, more than 300,000
Canadians live with the effects of stroke, and there are
50,000 new occurrences every year. 16,000 Canadians die
from stroke every year. Overall, stroke health care costs the
Canadian health care system $2.7 billion every year [6]. The
costs will only increase as the population continues to age.
It is possible to regain partial or complete motor function
through individualized rehabilitation programs. Traditionally,
Manuscript received January 12, 2007. This work was supported by the
Canadian Institutes of Health Research (CIHR), and the Natural Sciences
and Engineering Research Council of Canada (NSERC).
Stephen J. Ball is with Department of Electrical and Computer Engineer-
ing, Queen’s University, Kingston, ON, Canada.
Ian E. Brown is with the Department of Anatomy and Cell Biology, Cen-
tre for Neuroscience Studies, Queen’s University, Kingston, ON, Canada.
Stephen H. Scott is with the Department of Anatomy and Cell Biol-
ogy, Centre for Neuroscience Studies, Queen’s University, Kingston, ON,
therapists taught compensatory movements such as using
redundant joints of the body (i.e. using trunk motion to
assist with reaching) or fractionation of movements into
several simpler movements [5]. While compensation allows
patients to rapidly regain some degree of independence, a
strong reliance on compensation promotes learned non-use
of the impaired limb which slows or inhibits functional
recovery [12]. Current rehabilitation programs tend to focus
instead on reducing the degree of permanent disability.
Recovery of motor function has recently been linked to motor
learning that occurs during repetitive, frequent and inten-
sive movements [16]. This increased sensorimotor activity
takes advantage of neural plasticity, which is the ability of
adjacent areas of the brain to reorganize and compensate
for lost function in other brain regions. It is agreed that
exercising and practicing a variety of functional multi-joint
movements with the impaired limb is an important part of
therapy for stroke patients because it increases their ability
to perform activities of daily living [5]. Therefore, typical
therapy programs include the use of a variety of techniques
such as restraint, gravity compensation, manual guidance,
and progressive-resistive exercise.
Although these conventional techniques are effective, a
significant drawback is that they require strenuous manual
labour and extensive one-on-one attention from therapists.
As such, recovery is severely limited by staffing, time, and
budget constraints, and it is becoming more difficult to give
patients the time and attention that they require for maximum
recovery. Even without these limits, therapists can tire or
injure easily when manually moving heavy limbs, and with
no means to quantitatively record progress, it is a challenge to
properly monitor functional ability. Unfortunately, therapists
are often forced to resort to shorter, less intense therapy
programs that focus on teaching compensatory techniques
rather than on recovering motor function [3].
The ever increasing need for motor rehabilitation is strain-
ing the capabilities of the health care system. There is no
doubt that a more efficient system is required to provide the
high quality care that patients need. Robotic systems provide
a unique solution, and they offer a number of significant
advantages over conventional techniques. Robots can make
many precise movements with any level of assistance without
getting tired or making mistakes, allowing therapists to focus
on treatment planning and progress monitoring. Furthermore,
robots can provide a wealth of quantitative measurements
for every movement, which could lead to more sensitive
functional assessment scores. Other opportunities such as
home or group therapy (one therapist with multiple patients)
also become feasible using robotic technology.
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There is no question that robots may be ideally suited for
rehabilitation and there are a number of projects currently
underway that are trying to realize their potential for rehabili-
tation of the upper limb after stroke [7], [14]. Some existing
robots for upper limb rehabilitation and assistance include
MIT-MANUS [9], MIME [2], GENTLE/s [11], MULOS [8],
T-WREX [15] and ARMin [13] among others.
A significant drawback of current robotic devices is that
they cannot match the mobility of the human upper limb.
This is particularly true for the shoulder complex because it
has a compact arrangement of ve major degrees of freedom
(DOF): two at the sternoclavicular joint and three at the
glenohumeral joint. The glenohumeral joint can be approxi-
mated as a ball-and-socket joint and has been replicated in
some current devices. However, the shoulder girdle has been
neglected, despite its importance in stabilizing and orienting
the upper limb. Without direct control at the sternoclavicular
joint, it is not possible to prevent compensatory movements,
nor is there a means to properly regain strength and coor-
dination of the shoulder girdle. It seems that a next logical
step in assessing the usefulness of robotic technology in a
rehabilitation setting is to develop a robot that can more
closely match the mobility of the human shoulder.
There is no current robotic device that can independently
control all five DOF at the shoulder complex. As such,
MEDARM (Motorized Exoskelton Device for Advanced
Rehabilitation of Motor function) has been designed with
shoulder complex control as its fundamental goal. It is
intended to be used for assessment in addition to therapy.
Figure 1 shows MEDARM for the right upper limb. The
design objectives have been described previously [1], but the
key goals can be summarized as follows.
Independent control of ve DOF of the shoulder com-
plex (2DOF at the sternoclavicular joint, 3DOF at the
glenohumeral joint), and 1DOF at the elbow, with a
workspace similar to a typical upper limb workspace.
Actuators and exoskeleton sized for users from 1.4 m
to 2.0 m in height, and weighing up to 115 kg.
High backdriveability, low mass and inertia to minimize
influence on natural motion.
Allow simplification of the mechanism to 2DOF shoul-
der/elbow motion in any plane.
Avoid singular configurations across the workspace.
Maximize manipulability across the workspace.
Safe and comfortable for users with motor impairments.
Quick and easy to set up a patient.
MEDARM is an exoskeleton. An exoskeleton design was
chosen because it is the only way to independently control
all DOF in the shoulder complex, otherwise the redundancy
of the joints would make it impossible to isolate motion of
the glenohumeral joint from motion of the shoulder girdle.
Another advantage of the exoskeleton design is that grasping
a handle is not necessary, leaving the hand available for
Fig. 1. MEDARM system consists of a 6DOF robotic exoskeleton mounted
onto a support structure. The motors and electronics are mounted underneath
the robot, and external gravity compensation is provided by a motorized
vertical cabling system. A movable chair is used to bring the user into
alignment with the system.
functional training. The design phase of the MEDARM
project is now complete, as shown in Figure 1. The robot
is mounted to a support structure, and the user is wheeled
into position using a movable chair. There is space for the
operator to get beside the exoskeleton during the set-up
procedure. MEDARM consists of two main subsystems: the
shoulder/elbow mechanism (4DOF to move the upper arm
and forearm), and the shoulder girdle mechanism (2DOF
to move the glenohumeral joint relative to the torso). The
following describes the technical details these subsystems.
A. Shoulder/Elbow Mechanism
The shoulder/elbow mechanism (Figure 2a) is a 4DOF
mechanism consisting of a 3DOF spherical joint centred at
the user’s glenohumeral joint and a single rotary joint at the
elbow. It is actuated entirely by a cable-drive transmission
which is powered by five electric motors located on the
base of the system. The overall gear ratio for each of the
four joints is 8 so that the robot maintains backdriveability
without the need for force/torque sensors. The lightweight
mechanism is attached to the lateral side of the user’s arm
using two adjustable inflatable arm cuffs, which are the only
points of physical attachment to the user.
1) Joint Axis Orientation: Glenohumeral motion is
achieved using a spherical joint made from three intersecting
revolute joint axes. A problem with spherical joints is that it
is always possible to reach a singular configuration (where
one DOF is lost) by rotating the second joint so that the three
axes become coplanar. The order and relative orientation of
these three axes was optimized to ensure that the system
does not reach singularity within the user’s workspace (as
specified in [1]), that manipulability is maximized, and that
collision with the user or itself does not occur over the entire
workspace. The optimization process is described below.
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Joint #1 (
Joint #3 (
Joint (
Joint Centre
Joint #2 (
Link 1
Link 2
Link 3 Link 4
Joint #1
Joint #2
Joint #3
Fig. 2. The shoulder/elbow mechanism is cable-driven. (a) A CAD drawing
of the mechanism showing the final joint orientations and cable system. (b)
A simplified planar schematic representation of the optimal cable routing
structure. Each of the five cables is denoted by a different colour. Each joint
has a separate pulley for each cable that passes by the joint. Symbols s,
ξ, r, τ and θ represent cable displacement, cable force, pulley radius, joint
torque and joint angle respectively.
The first step in choosing the orientations of the axes
was to reduce the number of possible configurations by
considering the design objectives. In order for the last two
joints of the exoskeleton to operate in planar mode, it was
necessary to make the last (third) joint axis in the spherical
joint parallel to the elbow joint axis (see Figure 2a). With the
third joint axis orientation chosen, it was straightforward to
determine that the second joint axis should be perpendicular
to the third axis (and in the horizontal plane) in order to
avoid singularities in the workspace. This configuration also
has the added benefit of allowing basic flexion/extension or
adduction/abduction motions to be controlled using a single
joint axis.
To determine the optimal first joint axis orientation, it was
necessary to develop a simple iterative procedure to calculate
the box product, M, at each configuration in the workspace.
The box product is defined as:
M = z
× (z
× z
) (1)
where z
are the unit vectors corresponding to the joint
axes. When M = 1, the joint axes are orthogonal and
manipulability is maximized. When M = 0, the joint axis
are coplanar and a degree of freedom is lost (i.e. singular
right glenohumeral
nt centre
Abduction Angle (deg)
Box Product Maximum
Singular Abduction
Angle (
200 40 60 80
αα (deg) αα (deg)
ββ (deg)
ββ (deg)
Manipulability (M
200 40 60 80
Fig. 3. (a) The coordinate frame used for joint orientation optimization cal-
culations. The octant shaded in green approximates the humeral workspace.
(b) A plot of M for a given combination of α and β as θ
is varied to obtain
the singular abduction angle (θ
2(M =0)
) and the maximum manipulability
). (c) Plots of θ
2(M =0)
and M
for all combinations of α and
β. The range of α and β combinations that provides a suitable compromise
between θ
2(M =0)
and M
is shown by contour lines, and the overlap
is highlighted. (d) M
plotted radially over the workspace. Points closer
to the origin are configurations that are closer to singularity.
configuration). The procedure is summarized as follows, and
step-by-step results are shown in Figure 3:
1) The orientation of the first joint axis was defined rela-
tive to the second joint axis in terms of two variables
(α and β, as shown in Figure 2a).
2) With θ
and θ
fixed, manipulability (M) was calcu-
lated for a combination of α and β as θ
was varied
(corresponds to abduction, as shown in Figure 3b).
3) The singular abduction angle (θ
2(M =0)
) and the maxi-
mum manipulability (M
) were calculated and plot-
ted for all combinations of α and β (Figure 3c).
4) A range of α and β combinations that reached a
compromise between high M
and large θ
2(M =0)
was revealed (i.e. M
> 0.8 and θ
2(M =0)
> 120
The following iterative procedure was then used to
select a combination of α and β within this range.
5) M was calculated for the spherical joint workspace
for a given α and β (all three joints varied across their
ranges of motion, as shown in Figure 3d).
6) If any points were within 15
of singularity (M <
0.3) or if the exoskeleton could collide with the user,
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the process was repeated from step 5 using a different
combination of α and β.
7) The process was repeated until there were no singular-
ities in the workspace, and the manipulability was as
high as possible over the workspace.
The angles that provided the optimal spherical joint axes
arrangement are α = 45
and β = 40
. The maximum ma-
nipulability is 0.85 and averages 0.75 across the workspace.
2) Cable-Drive System: The joints of the shoulder/elbow
mechanism are actuated by electric motors with an open-
ended cable drive transmission. Cable-driven mechanisms
have a high power-to-weight ratio because all the motors can
be placed on the fixed base of the system. This significantly
reduces the size, mass and inertial properties of the robot, and
helps to reduce the motor torque output requirements. Open-
ended cable systems distribute loads across several cables,
which also reduces the the actuator requirements. Overall
the mechanism becomes more transparent to the user.
Additional transformations are required to control open-
ended cable-drive systems [17]. This is because the number
of joints needing control (n) is less than the number of
actuators (m). Cable systems can apply force through tension
only, so it is necessary to have an antagonistic cable routing
scheme for motion capability in both rotational directions
at each joint. As such, a minimum of n + 1 cables are
necessary for complete control of n joints. It is necessary
to have a positive tension in all cables at all times to prevent
the cables from becoming slack. Furthermore, since the
cables are routed along the entire length of the mechanism
through a series of pulleys, their motion affects multiple
joints, allowing loads at the joints to be distributed among
the actuators. Ultimately, joint angles and torques are related
to the length displacement and the forces in the cables.
The choice of cable routing scheme has a significant effect
on the performance of the device. In fact, for this 4DOF
system (n = 4) actuated by five motors (m = 5), there are
11 possible unique cable routing structures, all of which can
be described in matrix form. This structure matrix can be
analyzed to obtain quantitative measures related to efficiency
and actuator torque requirements [10]. Figure 2b illustrates
the optimal routing scheme which has minimized antagonism
between cables and hence the most even distribution of forces
across the cables, and also has the lowest peak forces.
3) Joint Design: Each joint of the exoskeleton requires a
low friction bearing system that provides rigidity against all
forces and non-axial moments. In addition to withstanding
non-axial gravitational and inertial moments during motion,
the joints must withstand substantial non-axial moments
resulting from forces applied by the cables and pulleys. Four-
point contact bearings are highly resistant to these moments
and therefore need not be used in pairs. Use of four-point
contact bearings in MEDARM has resulted in a thin and
lightweight exoskeleton.
B. Shoulder Girdle Mechanism
The shoulder girdle mechanism (Figure 4) provides 2DOF
about the sternoclavicular joint centre: elevation/depression
Joint #2
Joint #1
Sternoclavicular Joint Centre
Glenohumeral Joint Centre
Fig. 4. A CAD drawing of the shoulder girdle mechanism. The two joint
axes intersect at the user’s sternoclavicular joint. The second joint is a
translation along a curved track, producing a rotation about the vertical axis.
The joint is driven by a hinged linkage system. A single linear adjustment
shifts the entire shoulder/elbow mechanism to align the spherical joint with
the user’s glenohumeral joint centre.
and protraction/retraction. The entire mechanism is located
behind the user, and there is an adjustment to account for
users of different size. The mechanism supports the complete
shoulder/elbow system including the user’s arm, and as a
result must be structurally strong.
The first joint axis is fixed to the base structure behind
the user, with its axis pointing forward in the horizontal
plane. It is a conventional rotary joint that provides eleva-
tion/depression motion. The second joint axis is vertically
aligned, and intersects the first joint axis through the user’s
sternoclavicular joint centre, allowing protraction/retraction
motion. It is not a typical rotary joint; it is a curved track
system on which a carriage travels. The low-friction carriage
supports the entire cable drive system and is driven by a
hinged linkage system. The resulting mechanism operates
like a 4-bar linkage without requiring any structural elements
near the user’s sternoclavicular joint (see Figure 4). Both
joints are driven by electric motors with timing belts, and
operate with gear ratios of 5 and 6.25 respectively.
The benefits of this track system are significant. First,
it facilitates placing equipment behind the user rather than
above their head, which is safer and more comfortable for
the user, and also easier for the operator to set up. Second,
the hinged driving linkage doubles as a routing system for
the cables from the shoulder/elbow mechanism by guiding
them through to the base of the robot without any non-linear
changes in cable length. Any change in cable length as a
result of shoulder girdle motion is easily accounted for in
the cable length transformations.
The weight of this mechanism is substantial, and puts
high static torque requirements on the first shoulder girdle
joint. To assist the motor at this joint, an external gravity
compensation system is employed. A vertical motorized
cable is mounted directly above the end of the curved track
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(see Figure 1), and applies a vertical force on the track to
offset the gravitational forces on the MEDARM.
C. User Attachment and Alignment
To function correctly, the exoskeleton must be aligned with
the sternoclavicular and glenohumeral joints of the user, and
adjusted to fit arms of different lengths. A harness attaches
the user’s torso to a moveable chair which provides the
three translational adjustments necessary to align the user’s
sternoclavicular joint with the mechanism’s fixed shoulder
girdle joint centre. Once aligned, the chair is locked to the
main structure.
The mechanism must next be aligned with the user’s
glenohumeral joint centre. As before, three spatial adjust-
ments are required. However, this can be achieved by a
single manual linear adjustment because the redundancy of
the exoskeleton structure can be used to make the remaining
alignments. This linear adjustment shifts the cable-drive
system relative to the carriage in the direction approximately
aligned with the horizontal projection of the clavicle (see Fig-
ure 4) and is then clamped to the carriage. Thus modifying
the position of the mechanism’s glenohumeral joint centre
is achieved through the linear adjustment and the 2DOF
provided by the shoulder girdle. The 3DOF spherical joint
of the shoulder/elbow mechanism automatically compensates
by rotating until the mechanism is properly aligned with the
user’s limb.
This adjustment scheme has the benefit of simplifying
the structure of the shoulder girdle joint, and also the
set-up procedure. Otherwise, three consecutive translational
adjustments would be required, making the system sig-
nificantly larger, heavier and more complicated. Relying
on the shoulder/elbow mechanism to compensate for the
adjustment tends to push the shoulder joint away from its
optimal configuration, decreasing the range of motion of
the mechanism in some directions. However, the adjustment
range is typically small (2
or 3
at most), so the singularities
and manipulability of the mechanism will not be significantly
altered. Another issue that arises when adjusting a cable-
drive system is that it is necessary to maintain tension in the
cables at all times. Adjusting the link length must not change
the cable length, otherwise tension would be lost. Routing
the cables along the hinged driving linkage ensures that the
cable length does not change and that tension is maintained.
The exoskeleton system attaches to the user in two places:
the upper arm and the forearm (Figure 5a). These attach-
ments are to keep the exoskeleton aligned with the limb at
all times. The proposed design is to strap the limb into a rigid
half-cylindrical trough using an inflatable Velcro strap similar
to a blood pressure cuff. Once strapped in, the cuff is inflated
to provide a secure fit that is customized to the user. On the
lateral side of the cuffs is a single rigid connection to the
exoskeleton structure. The cuff will be attached to the subject
before connecting to the exoskeleton, which is easier for the
operator, and more comfortable for the user. An important
difference from many previous arm cuff designs is that the
arm cuff does not have a fixed size cuff through which the
Fig. 5. (a) A CAD drawing illustrating the arm cuff attachments and
adjustments. Each cuff has two translational adjustments to correctly align
the limb segments relative to the mechanism structure: perpendicular to
the link (small arrows) and parallel to the link (hollow arrows). A fifth
adjustment (large arrow) moves the location of the elbow joint to change
the length of the upper limb link. (b) A close-up of the cuff attachment,
showing the quick-release clamp.
user must put their arm. This allows simpler set up, and also
is compatible with a larger variety of arm sizes.
A total of five adjustments are required to ensure that
the user’s arm is properly aligned with the exoskeleton (see
Figure 5a). Each cuff is adjustable along the length of the
exoskeleton (for limbs of different length) and perpendicular
to the exoskeleton (for limbs of different width). The cuff is
attached by inserting it into a slider which can move freely
along the exoskeleton. A single quick-release clamp (similar
to those used to clamp bicycle components) simultaneously
clamps the cuff to the slider and the slider to the exoskeleton
(see Figure 5b). To accommodate users with different arm
lengths, a similar slider and clamp is used to locate the elbow
joint along the upper arm link. A passive hinged guide was
added to the upper arm link of the robot to ensure that tension
is not lost when adjusting the arm length.
Exoskeleton type devices always require more set up time
than their end-effector type counterparts. However, given its
mobility and adjustability, MEDARM has a relatively simple
set up procedure. In fact, once the chair is locked in place,
only four clamps are required to secure all eight adjustments.
This will keep set up time to a minimum, allowing the user
to receive a longer therapy session.
To make appropriate choices for the eight electric motors
required to actuate MEDARM, a dynamic model of the ex-
oskeleton and the human limb has been created in MATLAB
based on the robot toolbox [4]. The model was also used
to specify a number of other design parameters including
bearing strength, joint gear ratios, and cable load capacity.
The model takes the form of a standard rigid-body ma-
nipulator, and assumes that the cable dynamics are not
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Motor Static Torque (Nm) Peak Torque (Nm)
Shoulder Girdle #1 ±24 ±73
Shoulder Girdle #2 ±30 ±91
Glenohumeral #1 +39, 26 ±60
Glenohumeral #2 +39, 26 ±60
Glenohumeral #3 +39, 26 ±60
Elbow ±13 +40, 30
significant. Dynamic parameters of the exoskeleton including
lengths, masses and inertial properties are estimates from
CAD drawings. The same properties of the human upper
limb were calculated from anthropometric data tables based
on user height and weight [18] and are fully integrated
into the model. The model was adapted to account for the
external gravity compensation system, and includes estimates
of viscous and static friction. Given a trajectory for each
joint, the model calculates the joint torques required to
achieve that motion. The cable forces required to generate
these joint torques are then calculated using the torque
resolver technique [10]. The final output is the torque outputs
for all eight motors, the force in each cable, and all forces
and non-axial moments at each joint.
To get an estimate of the peak dynamic motor torques
for non-contact applications, the model was used to simulate
various reaching movements with a peak end-point velocity
of 1.0 m/s. Anthropometric limb measurements were chosen
to meet the maximum design requirements. Movements
included single joint movements through the full range of
motion of each joint, and a range of typical multi-joint reach-
ing movements such as reaching towards the face or chest
from a relaxed position. The most demanding positions for
the exoskeleton system in terms of static torque requirements
are those in which the arm is raised to the horizontal plane
with the elbow fully extended. The gravitational component
of the joint torques is the most significant contribution,
and produces the largest stresses on the motors in static
situations, so each position was held for one second to
facilitate measurements of peak static torque.
Motors and gear ratios were selected based on the results
of these simulations. The motors have built-in high resolution
encoders capable of measuring joint angle in increments of
. Each motor also incorporates an electric brake to
guarantee that the mechanism will not collapse during a
power failure. The brakes also ensure that the cables remain
in tension when the power is turned off. The simulations
also enabled selection of a braided stainless steel cable of
appropriate size, and also joint bearings with sufficient load
capabilities. The overall torque capabilities of each joint of
the exoskeleton are shown in Table I, and are a result of the
limits of both the motors and the cable strength.
This paper describes the design of a new robot for assess-
ment and rehabilitation of upper-limb motor function after
stroke. MEDARM is designed to be a versatile machine with
the potential to improve motor function of the proximal upper
limb. It is hoped that MEDARM will assist in prevention of
compensatory movements, while encouraging more natural
coordination for stroke patients of any degree of motor
impairment. The robot provides a large range of adjustments,
so it can easily accommodate users of varying shape and
size. MEDARM’s main advantage, however, is that it can
independently monitor and control all five of the main DOF
of the shoulder complex.
Efforts are currently focused on construction and testing
of a simpler 3DOF planar version of MEDARM to test out
the main principles of operation of the MEDARM design
including the curved track and cable-drive transmission.
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1-4244-1264-1/07/$25.00 ©2007 IEEE
... These systems are expensive and therefore difficult to find in rehabilitation centers, both private and public. Among the systems that have been proposed as robotic arms or exoskeletons for upper limb rehabilitation are: MIT-MANUS [6], ShouldeRO [7], MEDARM [8], NTUH-ARM [9], and CLEVER [10], among others. ...
Full-text available
Continuous passive motion (CPM) machines are used in the rehabilitation of members that have been injured to recover their range of motion and prevent stiffness. Nowadays, some CPM machines for the knee, ankle, arm, and elbow are available commercially. In this paper, ankle and shoulder rehabilitation robots, based on an X-Y table, are presented. The novelty of these rehabilitation robots is that they have a computerized numerical control system, resulting in low-cost machines. Some G-codes for basic and combined movement routines for ankle and shoulder rehabilitation are presented. In addition, the use of a robust generalized PI controller is also proposed to guarantee safe rehabilitation movements and compensate for passive stiffness in the ankle joint of stroke survivors. Some numerical simulations are included to illustrate the dynamic performance of the robust Generalized Proportional Integral (GPI) controller using the virtual prototype.
... However, due to the repetition of recommended exercises, the manual assistance is considered monotonous, time-consuming and fatigue prone for the physiotherapists [4,5]. Robotic assistance is considered to be more efficient, and several research prototypes have been designed to give upper-limb rehabilitation therapy [6][7][8][9][10][11]. Due to their limitations [4,12,13], only a few of these prototypes have been commercialised, as discussed below. ...
Purpose: Enormous assistance is required during rehabilitation activities, which might result in a variety of complications if performed manually. To solve this issue, several solutions in the form of assistive devices have been presented recently. Another issue highlighted is the lack of kinematic compatibility in low degrees-of-freedom (dof) systems. The proposed approach of developing a human-motion-oriented rehabilitation device deals with the problem through hybrid architectures. A novel modular synthesis approach is used for the purpose to induce generality in the design process. Materials and methods: Using a modular strategy, three planar hybrid configurations are generated for two-dof mechanisms for supporting flexion/extension motion. Three such architectures are optimally synthesised and kinematically analysed over the entire workspace. A Genetic Algorithm (GA) is used to synthesise the architecture parameters optimally. Moreover, the outcomes are evaluated against a set of seven poses and posture locations of the wrist to choose the most suitable configuration among the others. Subsequently, kinematic compatibility is analysed for the coupled system - formed by the selected architecture and the human arm - while wearing the proposed mechanism. Results: According to the findings of optimal synthesis, workspace and singularity analysis, configuration-III is capable of achieving the optimal postures for all task space locations (TSLs). Further, the work modifies the design by attaching additional three revolute passive joints for correcting misalignment concerns using coupled mobility analysis. Conclusion: The modular strategy for hybrid architectures and the subsequent mobility analysis provides an algorithmic framework for synthesising a task-based rehabilitation device.IMPLICATIONS OF REHABILITATIONManual physiotherapy is reported as repeated task, expensive and time-consuming, and considered stressful for the therapist or assistants to provide one-on-one physiotherapy to each patient in the traditional method. Robotic rehabilitation is, therefore, a viable option.In the several reported works on robotic rehabilitation exoskeletons, misalignment of the exoskeleton and the human motion is considered an open challenge. Normally, it is being managed through large number of degrees of freedom, which is certainly expensive and complex in control. The proposed approach of developing a human-motion-oriented rehabilitation device deals with the problem through hybrid architectures and modular strategy to develop them.While focusing upon the emulation of natural human motion trajectory, the compatibility of orthotic joint and human joint motion needs attention. As biological joint possesses complex kinematic characteristics, closed-loops are used in the design.Overall, a complete framework of a cost effective low-dof rehabilitation device is proposed and detailed through coupled analysis.
... Estos equipos generalmente hacen uso de mecanismos que cuentan con resortes para permitir, que independiente del ángulo de la articulación del robot, se logre disminuir el torque efectuado por la gravedad[6],[7].En la rehabilitación de patologías de miembros inferiores o superiores, se suelen usar sistema acoplados a las extremidades de la persona[8],[9], siendo exoesqueletos activos o pasivos, que en ocasiones hacen uso de sistemas de auto cancelación de la gravedad, como es el caso del prototipo desarrollado por Banala et al.[10], cuyo mecanismo cuenta con resortes embebidos en una estructura de soporte, que se conecta con el muslo y pantorrilla del sujeto. A pesar de ser sistemas que se integran directamente con la persona, por lo general se usan mecanismos con cables para redirigir y compensar las fuerzas de las extremidades, como es el caso de MEDARM, desarrollado por Ball et al.[11],[12], que es utilizado para la rehabilitación de lesiones en miembros superiores.1 2 3 4 5 ...
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En el contexto de la rehabilitación, la hidroterapia ha sido ampliamente promovida para el tratamiento de afecciones crónicas como artrosis, fibromialgia, control del peso, entre otros. Sin embargo, en ocasiones presenta contraindicaciones para pacientes que sufren de heridas abiertas, enfermedades infectocontagiosas, miedo al agua, entre otras; también, para el terapeuta la inmersión continua en agua puede acarrear inconvenientes ocupacionales. Como alternativa, el proyecto HYNMERS se concibe como un sistema constituido por un subsistema de realidad virtual y un prototipo mecánico pasivo, para proporcionar una sensación de ingravidez parcial en los miembros inferiores, emulando un tratamiento con terapia acuática, sin las contraindicaciones relacionadas con el contacto del agua, y presentándose como una opción más asequible a sistemas robóticos de rehabilitación. En este capítulo se presenta el proceso de diseño del subsistema mecánico pasivo, el cual se realiza a través de la identificación de los requerimientos del equipo, una búsqueda de alternativas que supliesen las condiciones de diseño y la ejecución de un proceso de conceptualización inicial, sobre el cual se desarrolló un constante proceso de rediseño y revisión, teniendo en cuenta la movilidad y anatomía del cuerpo humano, así como las posibles limitaciones constructivas y de ensamblaje. Para satisfacer el criterio de que el sistema no fuera motorizado, y aun así permitiese al usuario realizar ejercicios sin luchar contra la gravedad, se diseñó un sistema basado en poleas y contrapesos que permite la compensación del peso de los miembros inferiores y la ubicación de las poleas de acuerdo a la estatura del paciente; también facilita los movimientos de abducción y aducción de piernas. Es modular y fácil de ensamblar. Se presenta el prototipo fabricado y pruebas iniciales desarrolladas sobre el sistema, las cuales demuestran que este se encuentra en condiciones para continuar con fases posteriores de prueba con personas sanas y, eventualmente, con pacientes. 1. INTRODUCCIÓN En la actualidad, existen diversos casos de lesiones y patologías a nivel mundial que requieren de un proceso de rehabilitación física. Hay diversos tipos de rehabilitación, como la terrestre y la acuática, algunas de ellas, como la hidroterapia, incursionan cada vez con más fuerza y presentan un gran atractivo y potencial [1]. La terapia acuática, ha sido promovida por siglos con fines de rehabilitación [2]. La palabra se ha utilizado para describir una amplia gama de acciones, de las cuales la mayoría pertenecen a actividades terapéuticas y de ejercicio realizadas en piscinas climatizadas, se utiliza principalmente en entornos clínicos para el tratamiento, la rehabilitación y el manejo de afecciones crónicas como osteoartritis (OA) y fibromialgia, para el control del peso, entre otros. Actualmente, esta práctica también está ganando popularidad en entornos deportivos en áreas tales como rutinas de recuperación y para la rehabilitación de lesiones musculo esqueléticas agudas [3], [4]. El objetivo principal de la hidroterapia es ayudar a la rehabilitación de la función neurológica, musculo esquelética, cardiopulmonar y psicológica del individuo, con ejercicios que minimicen el impacto y favorezcan una terapia sin inconvenientes por el peso y otras condiciones fisiológicas del paciente. En algunos casos también ayuda a prevenir lesiones [5]. De hecho, es importante mencionar que la terapia acuática tiene ciertas contraindicaciones, por ejemplo, heridas abiertas, enfermedades infectocontagiosas, miedo al agua, cardiopatías descompensadas, bronquitis crónica descompensada, enfermedades micóticas, hipertensión arterial y varices, estados de debilidad extrema, enfermedades neurológicas o secuelas que imposibiliten la permanencia en la piscina [5]. Por otro lado, dentro del contexto del desarrollo de sistemas robóticos y mecatrónicos, los mecanismos de compensación gravitacional han sido ampliamente investigados, con el fin de reducir las cargas a los actuadores, siendo empleado en diferentes clases de robots, incluyendo sistemas utilizados en rehabilitación. Estos equipos generalmente hacen uso de mecanismos que cuentan con resortes para permitir, que independiente del ángulo de la articulación del robot, se logre disminuir el torque efectuado por la gravedad [6], [7]. En la rehabilitación de patologías de miembros inferiores o superiores, se suelen usar sistema acoplados a las extremidades de la persona [8], [9], siendo exoesqueletos activos o pasivos, que en ocasiones hacen uso de sistemas de auto cancelación de la gravedad, como es el caso del prototipo desarrollado por Banala et al. [10], cuyo mecanismo cuenta con resortes embebidos en una estructura de soporte, que se conecta con el muslo y pantorrilla del sujeto. A pesar de ser sistemas que se integran directamente con la persona, por lo general se usan mecanismos con cables para redirigir y compensar las fuerzas de las extremidades, como es el caso de MEDARM, desarrollado por Ball et al. [11], [12], que es utilizado para la rehabilitación de lesiones en miembros superiores. 1
... This robot structure consists of a base frame, a moving platform and a set of cables connecting in parallel the moving platform to the base frame [14]. CDPRs are well-known for their advantageous performance over classical parallel robots in terms of large translational workspace, reconfigurability, large payload capacity and high dynamic performance [15]. In literature several examples have been proposed. ...
This paper presents a new design of CADEL, a cable-driven elbow-assisting device, with light weighting and control improvements. The new device design is appropriate to be more portable and user-oriented solution, presenting additional facilities with respect to the original design. One of potential benefits of improved portability can be envisaged in the possibility of house and hospital usage keeping social distancing while allowing rehabilitation treatments even during a pandemic spread. Specific attention has been devoted to design main mechatronic components by developing specific kinematics models. The design process includes an implementation of specific control hardware and software. The kinematic model of the new design is formulated and features are evaluated through numerical simulations and experimental tests. An evaluation from original design highlights the proposed improvements mainly in terms of comfort, portability and user-oriented operation.
Upper extremity exoskeleton rehabilitation robots can be used for the training of patients with upper extremity motor dysfunction. In most cases, the design of such robots focuses on the configuration and the human-machine compatibility. For patients, the use of an exoskeleton rehabilitation robot mainly aims to improve their movement ability, which depends on the range of movement of the upper extremity joints. This paper proposes an eight-degree-of-freedom (DOF) upper extremity exoskeleton rehabilitation robot to improve the movement range of the patient’s upper extremity joints. The structural parameters of the shoulder joint are optimized and analyzed by the kinematic equations of the mechanism and the cyclic iteration algorithm such that the movement range of the patient joint can be maximized. The movement space of the robot is then simulated. Finally, the movement range of the rehabilitation robot joints and the movement space of the rehabilitation robot were measured. Experimental results show that the upper extremity exoskeleton rehabilitation robot can meet the patient’s shoulder, elbow, and wrist movement range, and the overlap with the human upper extremity movement space is 97.1 % and 95.7 % in the coronal and sagittal planes, respectively.
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Spinal Cord Injured (SCI) individuals and stroke patients, suffering from movement disorders of the upper limb, are often severely impaired in their quality of life and independence in Activities of Daily Living (ADLs). Functional Electrical Stimulation (FES) and robotic rehabilitation are popular and well-known means for enhancing modern therapy settings. Both systems, FES and robots, each have their specific advantages and drawbacks as, e.g., endless endurance of robotic systems versus occurring muscle fatigue during FES-assisted therapy. On the other hand, in contrast to robots, FES actively involves the patient’s muscles in the generation of movement. The combination of both techniques, also called hybrid neuroprosthesis, reveals a lot of new possibilities. This thesis presents new methods toward an adaptive hybrid neuroprosthesis for the upper limbs that utilizes the benefits of both, robot and FES, and overcomes the disadvantages by the respective other one. The cable-driven end-effector-based robot Diego by the company Tyromotion is extended by a four channel stimulation to form a novel hybrid neuroprosthesis for the upper limbs. The hybrid neuroprosthesis features a magnetometer-free sensor fusion method that overcomes the limited measurement information of end-effector-based robots by augmenting them with wearable inertial sensors. The evaluation with five healthy subjects demonstrates that the shoulder position and the elbow angle are accurately tracked. Furthermore, the sensor fusion method successfully detects undesirable compensatory shoulder movements. Thus, the hybrid motion tracking is well suited for performance assessment, real-time biofeedback, and feedback control of robotic and neuroprosthetic motion support. The practice of functional movements such as ADLs is assumed to improve the transfer of learned skills to daily life. Two different strategies for such training sessions are presented: a virtual environment that includes motivational aspects in the context of gamification, and a patient-triggered method, in which the patient is fully in charge of the control of applied FES and can freely determine the conducted movement sequence. The concepts motivate the patients to participate actively in the training sessions. The proposed methods’ technical and clinical feasibility is exemplarily demonstrated in experiments with three SCI subjects. Two different counterbalance-based control strategies are presented for the assistive weight support within the hybrid neuroprosthesis. They automatically adapt to the performed motion and current arm posture. First, inverse human arm models are implemented to counterbalance proportions of the arm weight using the robot’s rope forces. Additionally, a combined weight relief method that shares and automatically adapts the support between the robot and FES is proposed. The technical and clinical feasibility of the approaches and their advantages against constant robotic weight support are demonstrated in experiments and simulations. The hybrid neuroprosthesis furthermore provides a module for the FES-support of repetitive arm horizontal movements. An Iterative Learning Vector Field (ILVF) adjusts the stimulation intensities to the individual patient’s needs. Compared to previous iterative learning controllers, the main feature is that the patient is facilitated to perform the motion at self-selected cadence. The proposed learning algorithm explicitly takes the artificially activated muscles’ dynamics into account and assures smooth stimulation intensity profiles. The approach’s feasibility is successfully demonstrated in simulations with a complex neuro-musculoskeletal model. In total, the presented hybrid system and methods within this thesis address several open research issues in hybrid neuroprostheses contributing to a better adaptability to the patient’s needs and an intelligent sharing of the support between FES and the robot. These developments can improve the application of hybrid neuroprosthesis in the future and thus enhance the therapy outcome.
This chapter draws content from three literature reviews to provide an overview of the different types of humanoid and animal like robots used in health care settings. The factors that influence the acceptance of socially assistive robots by health and social care potential and actual users, family caregivers and healthcare professionals will be discussed with a special emphasis on culture. In addition, the current evidence on the views of healthcare professionals and the factors that impact on the implementation of these robots in health and social care environments will be presented.
This paper proposes the development of a seven degree-of-freedom (DOF) upper extremity exoskeleton to provide robotic therapy solutions for stroke survivors whose number is increasing along with the trend of ‘Aging Society’. Various robotic solutions have been illuminated and advanced along with their interfacing system in order to promote motor recovery after stroke. From this point of view, the proposed exoskeleton, RearMEX, is developed to (1) achieve active-actuation for the full range of human arm motions through the compact mechanical structure, (2) perform high force transparency through the reduction of the mechanical impedance, and (3) provide a user-interface for customized arm movements in active daily life. Especially, the exoskeleton system has a minimal impedance mode where a user can choose sequential desired postures for constituting a therapy motion by the simple button on the handgrip. Then, given a desired period for the movement, a novel interpolation method named norm-based time-allocating monotone Bézier interpolation is proposed to generate the corresponding trajectory with no jerk at each instant in the operational or configurational space. Furthermore, the disturbance observer (DOB) scheme is applied to achieve a robust tracking control performance on the interpolated trajectory even with model uncertainties and unexpected physical interactions with a wearer. The experimental results verify that the consistent performance can be achieved under various load conditions using the suggested controller.
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Frequent and repetitive functional training of the upper limb is a key aspect of regaining independence after stroke. Traditionally, this is achieved through manual one-on-one therapy, but patients are often unable to get sufficient treatment due to budget and scheduling constraints. An ideal solution may be robotic therapy, which is becoming an increasingly viable tool. Unfortunately, current rehabilitation robots ignore shoulder girdle motion, even though it plays a critical role in stabilizing and orienting the upper limb during everyday movements. To address this issue, a new adjustable robotic exoskeleton is proposed that provides independent control of six degrees of freedom of the upper limb: two at the sternoclavicular joint, three at the glenohumeral joint and one at the elbow. Its joint axes are optimally arranged to mimic natural upper-limb range of motion without reaching singular configurations and while maximizing manipulability across the workspace. This joint configuration also permits reduction to planar shoulder/elbow motion in any plane by locking all but the last two joints. Electric motors actuate the mechanisms using cable and belt transmissions designed to maximize the load capabilities of the robot while maintaining backdriveability and minimizing inertia. The device will be able to operate both as an assessment tool and as a therapy tool by monitoring and assisting movements. It will also be able to provide any level of gravity compensation. Controlling the entire shoulder complex facilitates training with more natural movements, with the added benefit of gaining the ability to observe and prevent compensatory motion.
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Our goal is to apply robotics and automation technology to assist, enhance, quantify, and document neurorehabilitation. This paper reviews a clinical trial involving 20 stroke patients with a prototype robot-aided rehabilitation facility developed at the Massachusetts Institute of Technology, Cambridge, (MIT) and tested at Burke Rehabilitation Hospital, White Plains, NY. It also presents our approach to analyze kinematic data collected in the robot-aided assessment procedure. In particular, we present evidence 1) that robot-aided therapy does not have adverse effects, 2) that patients tolerate the procedure, and 3) that peripheral manipulation of the impaired limb may influence brain recovery. These results are based on standard clinical assessment procedures. We also present one approach using kinematic data in a robot-aided assessment procedure.
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A major prerequisite for successful rehabilitation therapy after stroke is the understanding of the mechanisms underlying motor deficits common to these patients. Studies have shown that in stroke patients multijoint pointing movements are characterized by decreased movement speed and increased movement variability, by increased movement segmentation and by spatial and temporal incoordination between adjacent arm joints with respect to healthy subjects. We studied how the damaged nervous system recovers or compensates for deficits in reaching, and correlated reaching deficits with the level of functional impairment. Nine right-hemiparetic subjects and nine healthy subjects participated. All subjects were right-hand dominant. Data from the affected arm of hemiparetic subjects were compared with those from the arm in healthy subjects. Seated subjects made 40 pointing movements with the right arm in a single session. Movements were made from an initial target, for which the arm was positioned alongside the trunk. Then the subject lifted the arm and pointed to the final target, located in front of the subject in the contralateral workspace. Kinematic data from the arm and trunk were recorded with a three-dimensional analysis system. Arm movements in stroke subjects were longer, more segmented, more variable and had larger movement errors. Elbow-shoulder coordination was disrupted and the range of active joint motion was decreased significantly compared with healthy subjects. Some aspects of motor performance (duration, segmentation, accuracy and coordination) were significantly correlated with the level of motor impairment. Despite the fact that stroke subjects encountered all these deficits, even subjects with the most severe motor impairment were able to transport the end-point to the target. All but one subject involved the trunk to accomplish this motor task. In others words, they recruited new degrees of freedom typically not used by healthy subjects. The use of compensatory strategies may be related to the degree of motor impairment: severely to moderately impaired subjects recruited new degrees of freedom to compensate for motor deficits while mildly impaired subjects tended to employ healthy movement patterns. We discuss the possibility that there is a critical level of recovery at which patients switch from a strategy employing new degrees of freedom to one in which motor recovery is produced by improving the management of degrees of freedom characteristic of healthy performance. Our data also suggest that stroke subjects may be able to exploit effectively the redundancy of the motor system.
Conference Paper
Early intervention and intensive therapy improve outcome of neuromuscular disorder rehabilitation. However, a major problem is posed by considerable controversy surrounding the most appropriate method of therapy and there are still insufficient data to identify clearly the benefits of different approaches. At the same time largely still non-patient-specific methods for diagnosis and therapy are currently being used. Evidence indicates that where patient is motivated and premeditates his movement, the recovery is more effective and intelligent machines allow a broad scope to investigate these conditions. The ARMin robot is designed to assist, enhance, evaluate, and document neurological and orthopedic rehabilitation. Model-based impedance control enables the patient's effort being taken into consideration by allowing the machine to comply with forces exerted by the patient. The interaction is enhanced through a multimodal display based on visual, auditory, and kinesthetic modalities
Stroke is a leading cause of disability in particular affecting older people. Although the causes of stroke are well known and it is possible to reduce these risks, there is still a need to improve rehabilitation techniques. Early studies in the literature suggest that early intensive therapies can enhance a patient's recovery. According to physiotherapy literature, attention and motivation are key factors for motor relearning following stroke. Machine mediated therapy offers the potential to improve the outcome of stroke patients engaged on rehabilitation for upper limb motor impairment. Haptic interfaces are a particular group of robots that are attractive due to their ability to safely interact with humans. They can enhance traditional therapy tools, provide therapy “on demand” and can present accurate objective measurements of a patient's progression. Our recent studies suggest the use of tele-presence and VR-based systems can potentially motivate patients to exercise for longer periods of time. The creation of human-like trajectories is essential for retraining upper limb movements of people that have lost manipulation functions following stroke. By coupling models for human arm movement with haptic interfaces and VR technology it is possible to create a new class of robot mediated neuro rehabilitation tools. This paper provides an overview on different approaches to robot mediated therapy and describes a system based on haptics and virtual reality visualisation techniques, where particular emphasis is given to different control strategies for interaction derived from minimum jerk theory and the aid of virtual and mixed reality based exercises.
Thesis (Ph. D.)--University of Maryland at College Park, 1991. Thesis research directed by Dept. of Mechanical Engineering and Systems Research Center. Includes bibliographical references (leaves 113-115). Supported in part by the U.S. Dept. of Energy. Supported in part by the NSF Engineering Research Centers program.
The classic book on human movement in biomechanics, newly updated. Widely used and referenced, David Winter's Biomechanics and Motor Control of Human Movement is a classic examination of techniques used to measure and analyze all body movements as mechanical systems, including such everyday movements as walking. It fills the gap in human movement science area where modern science and technology are integrated with anatomy, muscle physiology, and electromyography to assess and understand human movement. In light of the explosive growth of the field, this new edition updates and enhances the text with: Expanded coverage of 3D kinematics and kinetics. New materials on biomechanical movement synergies and signal processing, including auto and cross correlation, frequency analysis, analog and digital filtering, and ensemble averaging techniques. Presentation of a wide spectrum of measurement and analysis techniques. Updates to all existing chapters. Basic physical and physiological principles in capsule form for quick reference. An essential resource for researchers and student in kinesiology, bioengineering (rehabilitation engineering), physical education, ergonomics, and physical and occupational therapy, this text will also provide valuable to professionals in orthopedics, muscle physiology, and rehabilitation medicine. In response to many requests, the extensive numerical tables contained in Appendix A: "Kinematic, Kinetic, and Energy Data" can also be found at the following Web site:
Incluye índice Incluye bibliografía Contenido: Introducción; Análisis de posición de manipuladores seriales; de manipuladores paralelos; Análisis Jacobiano; Estática y análisis de rigidez; Mecanismos de muñeca; Manipuladores movidos por tendones; Dinámica de manipuladores.