ChapterPDF Available

Humanoid Robot LOLA — Research Platform for High-SpeedWalking


Abstract and Figures

This paper describes the design concept of the performance enhanced humanoid robot LOLA. Our goal is to realize a fast, human-like walking motion. The robot has 22 degrees of freedom, including 7-DoF legs with actively driven toe joints. It is characterized by its lightweight construction, a modular, multi-sensory joint design with brushless motors and an electronics architecture using decentralized joint controllers. Special emphasis was paid on an improved mass distribution of the leg apparatus to achieve good dynamic performance. The sensor system comprises absolute angular sensors in all links, two custom-made force/torque sensors in the feet and a high-precision inertial sensor on the upper body. The trajectory generation and control system currently being developed aim at faster, more flexible, and more robust walking patterns.
Content may be subject to copyright.
Humanoid Robot LOLA– Research Platform for
High-speed Walking
Sebastian Lohmeier, Thomas Buschmann, Heinz Ulbrich, Friedrich Pfeiffer
Abstract This paper describes the design concept of the performance enhanced hu-
manoid robot LOLA. Our goal is to realize a fast, human-like walking motion. The
robot has 22 degrees of freedom, including 7-DoF legs with actively driven toe
joints. It is characterized by its lightweight construction, a modular, multi-sensory
joint design with brushless motors and an electronics architecture using decentral-
ized joint controllers. Special emphasis was paid on an improved mass distribution
of the leg apparatus to achieve good dynamic performance. The sensor system com-
prises absolute angular sensors in all links, two custom-made force/torque sensors in
the feet and a high-precision inertial sensor on the upper body. The trajectory gener-
ation and control system currently being developed aim at faster, more flexible, and
more robust walking patterns.
1 Introduction
Recent developments in enabling technologies (biped walking control, mechatron-
ics, computer technology) have lead to the design of sophisticated humanoid robots,
like ASIMO [5], HRP-2 [9] and WABIAN-2 [15]. Even if all robots achieve reli-
able dynamic walking —compared with human beings— high walking speeds still
remain challenging.
Obviously, the control problems inherent in fast walking are the most challenging
field, since there are still many unsolved problems, e.g. fast walking and running
[6,8], sudden turning motions, walking on rough terrain and trajectory generation in
complex environments. In our opinion, however, a careful design of the mechanical
hardware and the sensor system is just as essential, and and cannot be separated from
controller design. Rather, all components must be seen as tightly coupled parts of a
highly integrated mechatronic system. For example, the structural stiffness and mass
Institute of Applied Mechanics, Technische Universit¨
at M¨
unchen, 85748 Garching, Germany, e-
mail: {lohmeier,buschmann,ulbrich,pfeiffer}
2 Lohmeier et al.
Joint DoF
Head 2 (planned)
Shoulder 2
Elbow 1
Waist 2
Hip 3
Knee 1
Ankle 2
Toe 1
Total 22+2
Fig. 1 22-DoF humanoid robot LOLA (left) and kinematic configuration (right).
distribution can positively influence the dynamics of the overall system. Moreover,
the validity of model simplifications, e.g. the inverted pendulum model used in
the stabilizing controller, can be aided if disturbances by the highly accelerated leg
masses are minimized.
With the biped robot JOHNNIE which was developed at our institute from 1998
to 2003, a maximum walking speed of 2.4km/h has been achieved [10]. Fig. 1
(left) shows our new humanoid walking robot LOLA. The aim is to realize a fast,
human-like walking motion, including a significant increase in walking speed (goal:
5 km/h) and more flexible gait patterns. Furthermore, we want to increase therobot’s
autonomous, vision-guided walking capabilities. LOLA’s physical dimensions are
based on anthropometric data and correspond with a 180cm tall adult. The weight
of the robot is 55kg without batteries.
LOLA’s hardware approach tries to settle most of the technical problems discov-
ered in experiments with JOHNNIE and a thorough hardware analysis. The distin-
guishing characteristics of LOLA are its redundant kinematic structure with 7-DoF
legs, an extremely lightweight construction and a modular joint design using brush-
less motors. The sensor system was revised in order to improve signal quality and
bandwidth. In our opinion, one of the keys to faster walking is greater robustness
and stability. The new control architecture tries to achieve this by adding an on-line
adaptation of gait parameters such as step length and width in real-time (cf. [1]).
2 Design Concept
Fast locomotion still poses a significant challenge for humanoid robots and requires
an accurate design of the overall mechatronic system. Especially the legs and feet
Humanoid Robot LOLA– Research Platform for High-speed Walking 3
require careful engineering in order to achieve a good dynamic behavior. Since the
robot’s mass and its distribution have a strong influence on global system dynamics,
the lightweight construction is of great importance and must be balanced with the
demand for high stiffness and powerful drives.
2.1 Kinematic Structure
One of the most important conceptual challenges is the definition of a kinematic
structure, enabling a natural, stable and fast gait. From experiments and simula-
tions we have seen that additional, redundant DoF can increase the robot’s range
of motion, flexibility and stability of gait patterns and walking speed. Considering
results from biomechanical research on dynamics and kinematics of biped walking
(e.g. [3,14]) and experience with JOHNNIE [10] we chose a configuration with 22
actively driven DoF for LOLA (Fig. 1 right): The legs have 7 DoF each, while the
upper body has two and each arm has three DoF.
Nearly all humanoid robots are designed with 6-DoF legs —3 DoF in the hip, one
in the knee and two in the ankle. Each foot consists of one rigid body, therefore heel
lift-off during terminal stance phase can hardly be realized. Even small disturbances
lead to instabilities due to the line contact of the foot leading edge and the floor.
In human walking heel lift-off in the stance leg occurs during terminal swing, i.e.
shortly before the swing leg has floor contact [16]. Biped robots with one-piece foot
segments, however, cannot perform forward roll across the forefoot. Especially for
larger step lengths, this leads to an extended knee configuration at initial contact of
the swing leg resulting in large joint accelerations.
Therefore an additional, actively driven link between forefoot and heel, equiva-
lent to the human toes is proposed for LOLA. Heel lift-off in the stance leg allows the
swing leg to be in a more extended configuration. Area contact of the toe segment
stabilizes the robot and facilitates forward roll across the forefoot which is expected
to reduce the joint loads in hip and knee compared to a 6-DoF leg configuration.
There are only very few humanoid robots with actively driven toe joints, e.g. H6
and H7 [13]. Recently, OGURA ET AL. [15] presented the robot WABIAN-2 walking
with passive toe joints.
2.2 Further Requirements for High-speed Walking
Besides a suitable kinematical structure, further design goals can be defined to im-
prove the robot hardware for fast walking:
Minimum overall mass,
sufficient structural stiffness,
high center of gravity,
low moments of inertia of the leg links.
4 Lohmeier et al.
Obviously, the overall mass should be minimized, while a sufficient stiffness of the
robot’s structure must be maintained. This prerequisite is common to all mobile
robots with high dynamic demands.
Unlike humans, the largest portion of a biped robot’s weight resides in its legs,
since motors and gears determine approximately a third of the overall weight. There-
fore the center of gravity (CoG) height is lower than that of humans, i.e. typically
at the height of the hip joint or even below. According to the Linear Inverted Pendu-
lum Model (3D-LIPM) by KAJITA ET AL. [7], the CoG trajectory of the robot is a
piecewise hyperbolic curve, where the CoG lateral swing yCoG increases with lower
CoG positions:
yCoG coshrg
zCoG Ts
The 3D-LIPM illustrates the influence of the CoG height zCoG on the lateral swing
of the upper body during walking: Especially at higher walking speeds, the stability
of the robot increases when the lateral swing of the upper body is low. But mass
distribution in the legs not only influences CoG height, but also the inertia of the leg
segments. Therefore, during the final iteration of the mechanical hardware we chose
three additional measures to further improve mass distribution: First, we designed
the leg segments as investment cast parts using FE-based topology optimization
methods to achieve high stiffness at a minimal weight (Section 3.4). Moreover, by
choosing an appropriate kinematic actuation principle for the leg links, the mass
distribution can strongly be influenced: For the knee joint, a roller screw-based lin-
ear actuator is used (Section 3.2). The ankle joint is actuated by a 2-DoF parallel
mechanism with linear drives, where the motors are mounted on the thigh next to
the hip joint (Section 3.3).
3 Mechanical design
3.1 Modular joint concept
A detailed analysis by GIENGER [4] has revealed that structural components make
43 % of a humanoid robot’s weight. With approximately 31% the drive chains make
the second largest part, making the development of compact and lightweight joint
units a crucial factor. From the manufacturing and maintenance point of view, a fully
modular structure of the whole robot would be desirable, however, it collides with
the demand for minimal weight. For LOLA, all joints have the identical structure
with the sizes of gear and motor adapted to the requirements of each link. Many
parts are standardized for all drives, but some housings are specialized because of
weight and optimal load spread and distribution. This turned out to be the most
reasonable way to realize the robot at minimal weight while taking into account
ease of manufacturing [12].
Humanoid Robot LOLA– Research Platform for High-speed Walking 5
0 0.5 1 1.5 2 2.5 3 3.5 4
Continuous torque [Nm]
Spec. cont. torque [Nm/kg]
Maxon (Brush DC)
Bayside (PMSM)
DLR RoboDrive (PMSM)
Others (PMSM)
12 34
1 Stator winding 5 Incremental encoder
2 Motor shaft 6 Absolute angular sensor
3 Harmonic Drive gear 7 Limit switch
4 Cross roller bearing
Fig. 2 Left: Comparison of the power density of commercially available DC motors and PMSM.
Right: Mechanical design of Harmonic Drive based joints (e.g. Hip joint yaw axis)
To realize highly integrated joint units with maximum power density it is neces-
sary to use the latest technologies in the field of electrical drives, gears and sensors.
We are using high performance permanent magnet synchronous motors (PMSM)
from Parker Bayside because of their superior torque and speed capabilities (Fig. 2
left). The motors come as kit motors, which facilitates a space- and weight-saving
integration into the joint.
Except for the knee and ankle, all joints employ Harmonic Drive gears as speed
reducers, which are the de-facto standard for humanoid robots. Their advantages
are well known and include no-backlash and high reduction ratios at a low weight.
The compact design of Harmonic Drive component sets allows a space-saving inte-
gration directly into the joint units. All gears are custom lightweight versions with
a T-shaped Circular Spline which is, in our experience, the best tradeoff between
weight and loading capacity. The Wave Generators, modified for low weight and
inertia, are made from aluminum or steel. As an example, Fig. 2 (right) shows the
hip joint yaw axis.
3.2 Knee joint
Even though the torques and velocities are comparable, using the hip joint pitch
drive in the knee is problematic because its mass would unacceptably increase the
thigh moment of inertia. In turn a large part of the enhanced hip joint output would
be spent on accelerating a heavier thigh. By employing a roller screw-based linear
drive (Fig. 3 left), a better mass distribution in the hip-thigh area is achieved com-
pared to a Harmonic Drive based solution with identical performance: The thigh
inertia could be reduced by 65%, and the drive mass was reduced by more than
10%. Thus, the driving power of the knee could be enhanced without decreasing
the hip joint’s performance. The mechanism is nonlinear and the torque-speed char-
acteristic corresponds to the human knee (Fig. 3 right): The torque depends on the
6 Lohmeier et al.
1 Thigh 4 Motor
2 Shank 5 Roller screw
3 Knee joint 6 Universal joint
Fig. 3 Left: Knee joint with roller screw-based actuator. Right: Torque and speed requirements of
knee joint (Human torque capacity taken from [16])
link position and has its maximum at around 55, which is advantageous for typical
gait patterns of the robot. Conversely, maximum speeds increase at a stretched leg
configuration, where they are needed.
Compared to ballscrews that were used in our first designs [11], roller screws
have a significantly higher load rating which allowed us to further reduce the drive’s
weight. Moreover, due to their multi-point contact design, roller screws have the
ability to survive shock loads which makes them particularly suitable for the robot’s
3.3 Ankle joint
As shown in [11], both axes of the ankle joint show clearly different torque-speed
characteristics. By employing parallel drives, the required peak motor torque can
be reduced by approx. 35%. Different from our previous designs, where the drives
acted as length variable steering rods, the ankle joint drives were modified in the
final design which is shown in Fig. 4: The ankle joint (3) is actuated by two linear
drives (7) with the motors (4) mounted on the thigh (1) as close as possible to the
hip joint. Each linear drive (7) is connected to the motor (4) via a timing belt (5) and
a bevel gear (6) in the knee joint axis which is then connected to the roller screw
(8). Each linear drive consists of a roller screw (8) which is fixed to the shank, and a
linear bearing (9) which keeps the roller screw free from radial loads. A steering rod
(10) connects the roller screw nut and the foot segment. The incremental encoders
for motor control are mounted on the motor shaft, but the absolute angular sensors
(11) are mounted on the joint axes.
Humanoid Robot LOLA– Research Platform for High-speed Walking 7
1 Thigh 5 Timing belt 9 Linear guide
2 Shank 6 Bevel gear 10 Steering rod
3 Ankle joint 7 Linear drive 11 Angular sensor
4 Motor 8 Roller screw
Fig. 4 2-DoF parallel mechanism in the ankle joint of LOLA
3.4 Design of structural components
Both thigh and shank were designed as investment cast parts. By using Rapid
Prototyping-based manufacturing, there are almost no limitations of a component’s
shape and it is possible to realize complex, thin-walled components. As an example,
the design process of the shank is shown in Fig. 5. It connects the 1-DoF knee joint
and the 2-DoF ankle joint that are both actuated by roller screw drives. Therefore,
loads are transmitted not only at the joint flanges, but also at the hinging points of
the linear drives. Due to numerous points of force transmission of the linear drives,
thigh and shank show quite complex multi-axial stress conditions and strict geo-
metric constraints. Therefore we used the FEM-based topology optimization tool
OptiStruct to find an optimal design proposal which meets weight and/or stiffness
targets and other constraint criteria. Based on a mockup resembling the maximum
allowable designed space, an optimization model is built. Realistic results can only
be achieved if the force transmission by the roller screw drives is considered. There-
fore the thigh and the linear drives of knee and ankle are modeled as elastic bending
beams. The optimization result is the basis for the actual part design. After sev-
eral iterations of structural analysis and design refinement, the final geometry of the
component is developed. By using the original CAD data, the master pattern is made
by laser-sintering of plastic, which is then cast from aluminum.
8 Lohmeier et al.
Topology optimization CAD design Structural analysis Final component
Fig. 5 Development process of structural components based on topology optimization, for exam-
ple the shank.
4 Sensor system
4.1 Joint sensors
Each joint contains an incremental rotary encoder, an absolute angular encoder used
as link position sensor and a limit switch (cf. Fig. 2 right). The incremental rotary
encoder mounted on the motor shaft is mainly used for motor control. The absolute
angular encoder (resolution 17 bit, accuracy 0.1) compensates elasticities and non-
linearities in the drive chain and eliminates the need for a homing routine, making
startup faster and easier. To improve operational security and to prevent the robot
from self-destruction each joint incorporates a limit switch in the form of a light
4.2 Force/Torque sensors
LOLA is equipped with two six-axes force/torque sensors that are tightly integrated
into the foot structure. The required measurement range was determined using our
detailed multibody simulation model [2] for a walking speed of 5km/h. Based on
these data and multiple iterations of FEM-analyses, an optimal design of the sen-
sor body was developed (Fig. 6). The sensor consists of a single aluminum part
with four deformation beams in a classic “Maltese-cross” arrangement. Each beam
holds two pairs of strain gauges that operate in a half bridge configuration in order
to compensate for temperature dependency. Thin membranes mechanically decou-
ple the individual beam deflections to a far extent and reduce cross talk. In order
to protect the sensor from damage during experiments, we have integrated an over-
load protection. Mechanical end-stops engage into the flux of force at a vertical load
corresponding three times the weight of the robot and thus unload the sensitive mea-
surement beams. Special emphasis has been devoted to the strain gauge application.
Humanoid Robot LOLA– Research Platform for High-speed Walking 9
1 Ankle joint
2 Isolation
3 Measurement beam
4 Membrane
5 Strain gauge
6 Overload protection
7 Electronics
8 Connection to foot
Fig. 6 Schematic display of the 6-axis force/torque sensor (left) and the monolithic sensor body
before assembly (right).
The strain gauges are selected to match the elastic properties of the sensor material.
An exact application in combination with an appropriate temperature treatment fi-
nally lead to a high zero point stability of the signal. The calibration was done using
the least squares method. By applying more than 450 different load cases, a calibra-
tion error less than 0.5% could be achieved. At a total weight of 395g the sensor
includes all necessary electronics and a digital interface.
4.3 Inertial measurement unit
The inertial measurement unit (IMU) estimates the orientation and velocities of the
upper body. Simulations and experimental results with the robot JOHNNIE have
shown that the precision of this sensor significantly determines the performance of
the stabilizing controller. Therefore, the IMU must show high accuracy and a high
signal quality (i. e. low noise). Moreover, a low sensor bias results in a low long time
drift and a reliable calibration. We are using the inertial measurement unit iVRU-FC-
C167 (from iMAR Navigation) in a custom made lightweight version. The sensor
consists of three open-loop fiber-optic gyroscopes and three MEMS accelerometers.
The sensor fusion comprises internal error models and is integrated into the sensor,
which has a CAN interface.
5 Conclusions/Future Work
Despite recent advances, biped walking robots are still slow compared to humans
and have limited autonomy. The intention of the research presented here is to di-
minish this gap. This paper focused on the design concept of our new, 22-DoF hu-
manoid robot LOLA (180cm, 55 kg). LOLA’s distinctive features are an extremely
lightweight construction and a redundant kinematic configuration, which allows for
more flexible and natural motions. All joints are equipped with absolute angular
sensors and are driven by AC brushless motors through Harmonic Drive gears or
linear mechanisms with roller screws. The electronics architecture is designed as
10 Lohmeier et al.
an “intelligent sensor-actuator network” with a central controller. The new decen-
tral components increase the system’s performance from a technological point of
view. The trajectory generation and control system currently being developed aim
at faster, more flexible, and more robust walking patterns. In the near future, we will
integrate a camera head to enable autonomous locomotion. LOLA will serve as a
research platform for fast walking and visual-guided, autonomous walking.
Acknowledgements This work is supported by the “Deutsche Forschungsgemeinschaft” (grant
1. Buschmann, T., Lohmeier, S., Bachmayer, M., Ulbrich, H., Pfeiffer, F.: A collocation method
for real-time walking pattern generation. In: Proc. Int. Conf. Humanoid Rob. (Humanoids)
2. Buschmann, T., Lohmeier, S., Ulbrich, H., Pfeiffer, F.: Dynamics simulation for a biped robot:
Modeling and experimental verification. In: Proc. IEEE Int. Conf. Rob. Aut. (ICRA), pp.
2673–78 (2006)
3. Carson, M., Harrington, M.E., Thompson, N., O’Connor, J., Theologis, T.N.: Kinematic anal-
ysis of a multi-segment foot model for research and clinical applications: a repeatability anal-
ysis. J. Biomech. 34(10), 1299–307 (2001)
4. Gienger, M.: Entwurf und Realisierung einer zweibeinigen Laufmaschine. No. 378 in
Fortschrittberichte VDI, Reihe 1. VDI-Verlag, D¨
usseldorf (2005)
5. Hirai, K., Hirose, M., Takenaka, T.: The development of Honda humanoid robot. In: Proc.
IEEE Int. Conf. Rob. Aut. (ICRA), pp. 1321–26 (1998)
6. Honda Motor Co., Ltd.: New ASIMO - running at 6km/h (2005). URL http://world.
7. Kajita, S., Kanehiro, F., Kaneko, K., Fujiwara, K., Yokoi, K., Hirukawa, H.: A realtime pattern
generator for biped walking. In: Proc. IEEE Int. Conf. Rob. Aut. (ICRA), pp. 31–7 (2002)
8. Kajita, S., Nagasaki, T., Kaneko, K., Yokoi, K., Tanie, K.: A hop towards running humanoid
biped. In: Proc. IEEE Int. Conf. Rob. Aut. (ICRA), pp. 629–35 (2004)
9. Kaneko, K., Kanehiro, F., Kajita, S., Hirukawa, H., Kawasaki, T., Hirata, M., Akachi, K.,
Isozumi, T.: Humanoid robot HRP-2. In: Proc. IEEE Int. Conf. Rob. Aut. (ICRA), pp. 1083–
90 (2004)
10. L¨
offler, K., Gienger, M., Pfeiffer, F., Ulbrich, H.: Sensors and control concept of a biped robot.
IEEE Trans. Ind. Electron. 51(5), 972–980 (2004)
11. Lohmeier, S., Buschmann, T., Schwienbacher, M., Ulbrich, H., Pfeiffer, F.: Leg design for a
humanoid walking robot. In: Proc. Int. Conf. Humanoid Rob. (Humanoids) (2006)
12. Lohmeier, S., Buschmann, T., Ulbrich, H., Pfeiffer, F.: Modular joint design for performance
enhanced humanoid robot LOLA. In: Proc. IEEE Int. Conf. Rob. Aut. (ICRA), pp. 88–93
13. Nishiwaki, K., Kagami, S., Kuniyoshi, Y., Inaba, M., Inoue, H.: Toe joints that enhance bipedal
and fullbody motion of humanoid robots. In: Proc. IEEE Int. Conf. Rob. Aut. (ICRA), pp.
3105–10 (2002)
14. Novacheck, T.F.: The biomechanics of running. Gait & Posture 7, 77–95 (1998)
15. Ogura, Y., Shimomura, K., Kondo, H., Morishima, A., Okubo, T., Momoki, S., Lim, H.,
Takanishi, A.: Human-like walking with knee stretched, heel-contact and toe-off motion by
a humanoid robot. In: Proc. IEEE/RSJ Int. Conf. Rob. Sys. (IROS), pp. 3976–81 (2006)
16. Perry, J.: Gait Analysis – Normal and Pathological Function, 3rd ed. edn. Slack (1992)
... iki ayaklı robot yürüme deseni modellemesini ön izlemeli ZMP kullanarak elde etmişlerdir [15]. Münih Üniversitesinde 2003 yılında insansı robot Johnnie ve 2009 yılında ise Lola geliştirilmiştir [16,17,18,20]. Boston Dynamics firması tehlikeli işler için Petman'ın yanı sıra denge dinamiği ileri derecede olan ATLAS isimli iki ayaklı yürüyen robotları geliştirmiştir [6,21]. ...
... Bu çalışmada daha çok iki bacaklı robotlardaki eklemlerin sayısının fazla olmasının ve eklemlerinin kontrolünün zorluğunu bertaraf edecek statik yürüme deseninin uygulama detayları irdelenmiş ve statik yürüme deseninin elde edilmesine odaklanılmıştır. Esasında Asimo [2,3,9,10], Johnnie ve Lola [16][17][18][19] ve Atlas [6] gibi popüler robotların yürüme desenleri de benzerdir, ancak bu robotların esas farkları denge kontrol dinamiğine sahip olmalarıdır. Sonuç olarak statik yürüme her ne kadar literatürde en çok kullanılan bir yöntem olsa da bu çalışmanın iki ayaklı robotlar için yürüme deseni üretilmesinde eğitici bir uygulama özelliği olması amaçlanmıştır. ...
Full-text available
Robotik bilimi, teknolojinin gelişmesiyle birlikte büyük bir ivme kazanmıştır. Bu nedenle, büyük teknoloji ve otomotiv üreticileri insanın yürümesine benzeyen robotları günlük yaşama entegre etmek için birbirleriyle yarış halindedirler. Bu firmaların ürettikleri iki ayaklı robotların yürümesi zamanla insanın yürümesine benzemeye başlamıştır. Ancak, insanın yürümesindeki eklem sayılarının çok olması iki ayaklı robotlar için yürüme deseni oluştulmasını zorlaştırdığı için iki ayaklı robotlar için göze hoş gelen yürüme deseni oluşturulması kolay değildir. Bu çalışmada, doğada iki ayak üzerinde en güzel yürüyen canlı olan insandan esinlenerek yapılan iki ayaklı robotta 12 eklem için 12 adet akıllı servo motor kullanıldı. Robotun elektrikli, elektronik ve mekanik modelini elde etmek için kalçada 3, dizde 1 ve ayak bileğinde 2 olmak üzere toplam 6 adet akıllı servis motoru kullanıldı. Kinematik modeli oluşturulduktan sonra ise fizik, matematik ve geometrik yöntemler kullanılarak iki ayaklı robotun statik yürüme deseni oluşturuldu. Statik yürüme deseninin eklem açıları üretildikten sonra ise bu açıların değerleri açık kaynak kodlu derleyicide programlandı ve elektronik mikrodenetleyiciye yüklendi. Daha sonra mikrodenetleyicinin çalıştırılmasıyla iki ayaklı robotun eklemlerinde bulunan akıllı servo motorların bir harmoni içinde çalıştığı ve iki ayaklı robotun statik yürümesini düşmeden başarılı bir şekilde gerçekleştirildiği gözlemlendi.
... With three degree of freedom ( around pitch, yaw and roll axes) for the human being, these joints play a very important role during walking and manipulating tasks. In the last decade, many active humanoid robots such as HRP series (2, 3 and 4) [3], HONDA Ashimo [4], TOYOTA humanoid [5], H7 [6], Johnnie and LOLA [7], HUBO series [8], NAO [9], ICub [10] , WABIAN-2 [11], CB [12] and ROBIAN biped [13] have been built. For all these robots, the design of either ankle or wrist joints, raises usually two global questions to answer. ...
... On the kinematic point of view, the most known ankle or wrist joints are built with serial mechanisms. Few solutions are based on parallel mechanisms [7], [13], [19], [20], but remain with only two active DOF (e.g. pitch and yaw). ...
Full-text available
This paper deals with the design of a new class of hybrid mechanism dedicated to humanoid robotics application. Since designing and control of humanoid robots are still open questions, we propose the use a new class of mechanisms in order to face several challenges which are mainly the compactness and the high power to mass ratio. Human ankle and wrist joints can be considered of the more compact with the highest power capacity and the lowest weight. The very important role played by these joints during loco-motion or manipulation tasks makes their design and control essential to achieve a robust full size humanoid robot. The analysis of all existing humanoid robots shows that classical solutions (serial or parallel) are usually used leading to bulky and heavy structures. To face these drawbacks and get a slender humanoid robot, a novel 3 Degrees Of Freedom (3-DOF) hybrid mechanism achieved with serial and parallel substructures with a minimal number of moving parts is proposed. This hybrid mechanism able to achieve pitch, yaw and roll movements can be actuated either hydraulically or electrically. For the parallel sub-mechanism, the power transmission is achieved thanks to cables which allow the alignment of actuators along the shin or the forearm main axes. Hence, the proposed solution fulfils the requirements induced by both geometrical, power transmission and biomechanics (range of motion) constraints. All stages including kinematic modeling, mechanical design and experimentation using the HYDROïD humanoid robot's ankle mechanism are given in order to demonstrate the novelty and the efficiency of the proposed solution.
... Additional complexity was added to decouple the individual beam deflections, resulting in reduced cross-talk on the sensors. A similar method was used in [7], [8] where they used four deformation beams, with each beam holding two strain gauges. ...
Full-text available
After analyzing dynamic motions performed in nature, it is clear that animals adapt their footing in real time to compensate for disturbances such as slipping or stumbling, by relying on ground reaction force feedback. However, in robotics, this feedback is not commonly utilized due to the costs, as well as the size and mass of available ground reaction force sensors. The aim of this letter is to present a prototype of a novel ground reaction force sensor that makes use of low-cost load cells mounted at fixed angles to each other. The angle of the load cells was chosen to maximize crosstalk between the sensors while minimizing the overall size of the sensor. Due to the crosstalk, it drastically simplified the mechanical design of the sensor. Through the use of neural networks, two-axis ground reaction forces were estimated with a high accuracy of above $98.5\%$ . Future research involves extending the concept to measure three-axis ground reaction forces in real time.
... The preset limit of 130 Nm is three-to-four times the amount of torque needed for a regular walk of humans [6,38]. Although that might seem high, the research has shown that humans are able to achieve such high torques [1], so can robots (for example, state-of-the-art humanoid robot Lola [21] can achieve such high torques). This means that the proposed framework is generating physically realistic motions that can be performed by both humans and modern humanoid robots. ...
Full-text available
The main indicator of dynamic balance is the \(\mathit{ZMP}\). Its original notion assumes that both feet of the robot are in contact with the flat horizontal surface (all contacts are in the same plane) and that the friction is high enough so that sliding does not occur. With increasing capabilities of humanoid robots and the higher complexity of the motion that needs to be performed, these assumptions might not hold. Having in mind that the system is dynamically balanced if there is no rotation about the edges of the feet and if the feet do not slide, we propose a novel approach for testing the dynamic balance of bipedal robots, by using linear contact wrench conditions compiled in a single matrix (Dynamic Balance Matrix). The proposed approach has wide applicability since it can be used to check the stability of different kinds of contacts (including point, line, and surface) with arbitrary perimeter shapes. Motion feasibility conditions are derived on the basis of the conditions which the wrench of each contact has to satisfy. The approach was tested by simulation in two scenarios: biped climbing up and walking sideways on the inclined flat surface which is too steep for a regular walk without additional support. The whole-body motion was synthesized and performed using a generalized task prioritization framework.
... In current robotics research, an increasing number of humanoid robotics platforms have been developed [2,6,11,14,18,20,23,28]. One of the recent robots is the Myon robot [11], built as part of the EU project ALEAR. ...
Technical Report
Full-text available
Developing neural networks for the behavior control of au- tonomous robots can be a time-consuming task. This is especially the case for the new generation of complex robots with many sensors and mo- tors – such as humanoid robots –, for which the networks with hundreds of neurons can become comparably large. Looking at the correspond- ing controller design workflow, a number of properties can be identified that slow down the development process: (1) The difficulty to create, handle and comprehend the large neuro-controllers, (2) the intricate de- bugging of neuro-controllers on the hardware, (3) delays caused by fre- quent time-consuming uploads of controllers to the hardware, (4) poten- tial damaging of the robot and (5) the overall maintenance effort. This article proposes several measures to improve this workflow with respect to the mentioned problems. Some proposed improvements are realized by using sophisticated evolutionary robotics development software and suitable graphical network design tools. Such software, here in particu- lar the Neurodynamics and Evolutionary Robotics Development Toolkit (NERD), significantly improves the network design process, specifically by allowing the development partially in simulation, by allowing a visual design of controllers with graphical network editors and by using suited neuro-evolution algorithms. Other improvements are based on proper neuro-modules that can be used to increase the usability of existing con- trollers. Bundled together, the proposed measures lead to a faster devel- opment of neuro-controllers. The proposed methods are demonstrated exemplarily with the Myon humanoid robot, but they can be applied also to other robots with similar properties and thus can help to improve the workflow for the neuro-controller design on such robot hardware.
... Actuation of robotic system such as humanoid robots is basically based on two major solutions: (1) Electric; and (2) Hydraulic. Electric actuation is typically used for humanoid robots, like HRP series (2, 3 and 4) [1]; HONDA ASIMO [2]; TOYOTA humanoids [3]; H7 [4]; Johnnie and LOLA [5]; HUBO series [6]; NAO [7]; iCub [8]; WABIAN-2 [9] and ROBIAN biped [10]. It is worthy to note that electric actuators have the advantages of reduced cost and their easiness of usage and control. ...
We design a new high performance integrated electro-hydraulic actuator (IEHA). We propose a new solution to a still open question in robotics, to provide an efficient and compliant actuation. The proposed actuator, which is dedicated to motorize independently each joint of a robotic system is designed to be fixed as near as possible to the joint itself, enhancing the performances while reducing the usual drawbacks of classical hydraulic actuation. The novel IEHA contains an integrated micro-pump with a floating barrel allowing the inversion of the flow direction without inverting the rotation of the input electric motor. The integration of a micro-valve and a rotary hydraulic distributor ensure the compactness of the proposed solution. In this paper, first, the proposed hydraulic actuation principle is given in detail. Then the designed prototype and the first experiments are presented demonstrating the novelty and the efficiency of our solution.
Recent advances in mobility, manipulation, and intelligence of robots have promoted the usability of humanoid robots to support humans in their daily lives in the future. The multi-axis force-torque sensor is an essential sensor for the biped humanoid robot to maintain balance during walking and running since it is used to calculate the zero-moment point, the criterion of dynamic stability. Force-torque sensors will be widely used in the future because they are essential for service robots to interact with people in unstructured environments. However, due to special design considerations and requirements, it is difficult to find a suitable commercial force-torque sensor for biped humanoid robots, and the price is very expensive. This paper reviews the multi-axis force-torque sensor used in current state-of-the-art humanoid robots based on the understanding of biped walking, zero-moment point and ground reaction force. From an in-depth analysis of relevant information, sensor requirements are discussed with the robot performance. In addition, the structural design of the sensors is classified into four types and described in detail. This comprehensive review will facilitate the development of force-torque sensors in humanoid robots and will be helpful in extending their application in the various fields of service robots.
Hydraulics is an old technology which is being applied in many applications including large machinery, heavy industries, and early robotics. The traditional features of hydraulics that possess a high power to weight ratio compared to other power transmission system make it suitable to work in a tough and robust environment. However, the trend of hydraulic system has decreased since the introduction and mass usage of the powerful brushless motor and rare earth magnetic motor in industrial sector since the 1980s. Recently, hydraulic systems have shown incremental demand where the innovation of hydraulic actuators and components was actively conducted aimed at compactness, lightweight with higher energy-efficiency, clean and friendly features for many applications in both mobile and industrial hydraulics. This review shows the hydraulic trends in tough robotics applications which focus on legged robots such as humanoid, search and rescue robot and large machinery. New innovations of hydraulic components such as actuators, pump, and other accessories and trends are discussed for future hydraulics in tough robotics applications.
This paper proposes the novel force control method based on higher-order derivative for high-backdrivable actuation of the robot employing elastomer-based series elastic actuators (SEAs). Control of SEAs is generally difficult because they consist of an underactuated 2-inertia system. Previously, we control it with a position control method. Lately, we employ a torque control method to overcome several problems. The new one enable robot to be controlled more easily, safely and efficiently. To evaluate this method, the experiments of previous position control method, conventional force control method, and proposed force control method are performed.
Full-text available
The paradox of Painlevé occurs when the dynamics of a sliding rigid body has solution inconsistency. When approaching a configuration of inconsistency, the contact forces and accelerations may grow unbounded in finite time, a scenario which is called dynamic jamming. Painlevé’s paradox was originally formulated for a sliding rod with uniform mass distribution, for which inconsistency occurs only under unrealistically high contact friction conditions. This paper shows that when the sliding rod is replaced by a sliding mechanism, the dynamic jamming predicted by Painlevé’s paradox can occur under relatively low friction. The paper proposes a particular mechanism, called IPOS, which consists of an inverted pendulum hinged to a plate that slides on an inclined plane (IPOS = Inverted Pendulum On a Slider). The IPOS mechanism can reach solution inconsistency under practical friction conditions, and can thus be used to experimentally validate the theoretical predictions. The conditions under which dynamic jamming occurs in the IPOS mechanism dynamics are explicitly derived, and numerical simulations illustrate the feasibility of dynamic jamming experiments. KeywordsNonsmooth mechanics–Painlevé’s paradox–Multibody dynamics–Frictional contact
Conference Paper
Full-text available
This paper presents a new real-time walking pattern generator that calculates center of mass trajectories from footstep locations. Key features are the calculation of reference torque patterns by quadratic programming and the solution of the equations of motion by spline collocation. Fast real-time planning is combined with offline optimisation of free parameters based on a comprehensive simulation of the closed loop system to automatically generate optimally tuned walking controllers. The effectiveness of the proposed method is shown using a dynamics simulation of the robot JOHNNIE.
Conference Paper
Full-text available
Addresses the extension of a humanoid's action capability by attaching toe joints. The effectiveness of toe joints is discussed in three aspects. One is utilizing it to speed up the walking, another is using it to enable a humanoid to go up higher steps, and the other is using it to whole-body action in which knees are contacting the ground. Feet with toe joints are developed for humanoid 'H6'. An experiment of the wholebody action in which knees are contacting the ground is carried out to show the usefulness of toe joints for such actions. Then the walking pattern generation system is extended to use toe joints. Using this extended system maximum speed of knee joints can be reduced at the same walking speed, and 80% faster walking speed is achieved on humanoid 'H6'
This text encompasses the work of Dr Jacquelin Perry in her years as a therapist and surgeon focusing on the human gait. The text is broken down into four sections: fundamentals; normal gait; pathological gait; and gait analysis systems. In addition to the descriptions of the gait functions, a representative group of clinical examples has been included to facilitate the interpretation of the identified gait deviations. The book includes detailed laboratory records with illustrations and photographs. Intended as a reference for health care professionals involved in musculoskeletal patient care, the text is suitable for incorporating into many athletic training programmes, university physical therapy programmes and gait workshops.
Conference Paper
Dynamics simulation is a valuable tool for biped robot hardware and controller design. Due to the complexity of biped walking robots, simulation times can be quite high. It is therefore important to identify the key components in modeling the system so that the phenomena of interest can be correctly predicted at a reasonable numerical cost. In this paper a detailed and a reduced simulation of the biped robot JOHNNIE are presented and results are compared with experimental data. The comparison shows that results for both models correctly predict global dynamics of the system, while some phenomena are only captured by the more complex model
Conference Paper
The paper presents the leg design of the 22-DoF humanoid walking robot Lola. The goal of the project is to realize a fast, human-like walking motion. The robot is characterized by its lightweight construction, a modular, multi-sensory joint design with brushless motors and an electronics architecture using decentralized joint controllers and sensor data processing. Linear actuators are used for the knee and ankle joints to achieve a better mass distribution in the legs and to improve performance of the stabilizing control. Some critical structural parts have been designed by means of topology optimization in order to balance the demands for high stiffness and strength with low weight
Conference Paper
The paper presents the performance enhanced humanoid robot LOLA which is currently being manufactured. The goal of the project is the realization of a fast, human-like walking motion. The robot is characterized by its lightweight construction, a modular, multi-sensory joint design with brushless motors and an electronics architecture using decentralized joint controllers. The fusion of motor, gear and sensors into a highly integrated, mechatronic joint module has several advantages for the whole system, including high power density, good dynamic performance and reliability. Additional degrees of freedom are introduced in elbow, waist and toes. Linear actuators are employed for the knee joints for a better mass distribution in the legs
Conference Paper
A humanoid robot, WABIAN-2R, capable of human-like walk with stretched knees and heel-contact and toe-off motions is proposed in this paper. WABIAN-2R has two 1-DOF passive joints in its feet to enable it to bend its toes in steady walking. Further, it has two 6-DOF legs, a 2-DOF pelvis, a 2-DOF trunk, two 7-DOF arms with 3-DOF hands, and a 3-DOF neck. In addition, a new algorithm for generating walking patterns with stretched knees and heel-contact and toe-off motions based on the ZMP criterion is described. In this pattern generation, some parameters of the foot trajectories of a biped robot are optimized by using a genetic algorithm in order to generate a continuous and smooth leg motion. Software simulations and walking experiments are conducted, and the effectiveness of the pattern generation and mechanism of WABIAN-2R, which have the ability to realize more human-like walking styles in a humanoid robot, are confirmed
This review article summarizes the current literature regarding the analysis of running gait. It is compared to walking and sprinting. The current state of knowledge is presented as it fits in the context of the history of analysis of movement. The characteristics of the gait cycle and its relationship to potential and kinetic energy interactions are reviewed. The timing of electromyographic activity is provided. Kinematic and kinetic data (including center of pressure measurements, raw force plate data, joint moments, and joint powers) and the impact of changes in velocity on these findings is presented. The status of shoewear literature, alterations in movement strategies, the role of biarticular muscles, and the springlike function of tendons are addressed. This type of information can provide insight into injury mechanisms and training strategies. Copyright 1998 Elsevier Science B.V.
An unbiased understanding of foot kinematics has been difficult to achieve due to the complexity of foot structure and motion. We have developed a protocol for evaluation of foot kinematics during barefoot walking based on a multi-segment foot model. Stereophotogrammetry was used to measure retroreflective markers on three segments of the foot plus the tibia. Repeatability was evaluated between-trial, between-day and between-tester using two subjects and two testers. Subtle patterns and ranges of motion between segments of the foot were consistently detected. We found that repeatability between different days or different testers is primarily subject to variability of marker placement more than inter-tester variability or skin movement. Differences between inter-segment angle curves primarily represent a shift in the absolute value of joint angles from one set of trials to another. In the hallux, variability was greater than desired due to vibration of the marker array used. The method permits objective foot measurement in gait analysis using skin-mounted markers. Quantitative and objective characterisation of the kinematics of the foot during activity is an important area of clinical and research evaluation. With this work we hope to have provided a firm basis for a common protocol for in vivo foot study.