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The author obtained his Ph. D. in 1986 under Professor Bernard Roth. In a publication from the research, it was shown that the redundant joints in a serial robot could be used to make the end-effector linear velocity distribution isotropic. In this work we revisit those results, present recent results on how redundancy is made use of in a human arm...
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... quantify the redundancy in the human arm during the point-to-point planar movements, we assume a model of the human arm as shown in figure 7. The model is different from the human arm shown in figure 3 in two main ways -a) due to the experimental set-up the portion of the body above the shoulder also moves and we need to take into account this motion, and b) the motion of the robot and the hand is purely planar. ...
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Citations
... As a result of that, the total degrees of freedom (DoF) of the human model is not exact. For example, the human arm is modeled as 4 DoF in Theofanidis et al. (2016), 9 DoF in Phan et al. (2017 and 7 DoF in Ghosal (2018). ...
Human-robot cooperation (HRC) is becoming increasingly relevant with the surge in collaborative robots (cobots) for industrial applications. Examples of humans and robots cooperating actively on the same workpiece can be found in research labs around the world, but industrial applications are still mostly limited to robots and humans taking turns. In this paper, we use a cooperative lifting task (co-lift) as a case study to explore how well this task can be learned within a limited time, and how background factors of users may impact learning. The experimental study included 32 healthy adults from 20 to 54 years who performed a co-lift with a collaborative robot. The physical setup is designed as a gamified user training system as research has validated that gamification is an effective methodology for user training. Human motions and gestures were measured using Inertial Measurement Unit (IMU) sensors and used to interact with the robot across three role distributions: human as the leader, robot as the leader, and shared leadership. We find that regardless of age, gender, job category, gaming background, and familiarity with robots, the learning curve of all users showed a satisfactory progression and that all users could achieve successful cooperation with the robot on the co-lift task after seven or fewer trials. The data indicates that some of the background factors of the users such as occupation, past gaming habits, etc., may affect learning outcomes, which will be explored further in future experiments. Overall, the results indicate that the potential of the adoption of HRC in the industry is promising for a diverse set of users after a relatively short training process.
... Usually, redundancy resolution in velocity space is achieved by the generalized Moore-Penrose inverse (pseudo-inverse), which minimizes the quadratic norm of joint rates for a desired translational and angular velocity of the end effector. The complexity of the pseudoinverse of a manipulator Jacobian matrix is O(3) [1], which can become inefficient for hyper-redundant systems, such as snake-like robots or continuum robots [2]. Nevertheless, velocity pseudo-inverse approaches are popular because they provide universal, robotindependent, and well-documented solutions [3][4][5][6]. ...
This work proposes a solution for redundant nonholonomic mobile manipulator control with corridor constraints on base motion. The proposed control strategy applies an artificial potential field for base navigation to achieve joint control with desired trajectory tracking of the end effector. The overall kinematic model is created by describing the nonholonomic mobile platform and the kinematics of the manipulator. The objective function used consists of a primary control task that optimizes the joint variables to achieve the desired pose or trajectory of the end effector and a secondary control task that optimizes the joint variables for the base to support the arm and stay within the corridor. As a last priority, an additional optimization is introduced to optimize the maneuverability index. The proposed baseline navigation has global convergence without local minima and is computationally efficient. This is achieved by an optimal grid-based search on a coarse discrete grid and a bilinear interpolation to obtain a continuous potential function and its gradient. The performance of the proposed control algorithm is illustrated by several simulations of a mobile manipulator model derived for a Pal Tiago mobile base and an Emiko Franka Panda robotic manipulator.
... For redundant robots, determining analytically all solutions of the inverse kinematics problem is a very difficult task [8][9][10][11]. Despite the complexity, [8][9][10][11] contain several examples of finding solutions analytically. The Pioneer 2 robotic arm is a redundant robot with five degrees of freedom. ...
... For redundant robots, determining analytically all solutions of the inverse kinematics problem is a very difficult task [8][9][10][11]. Despite the complexity, [8][9][10][11] contain several examples of finding solutions analytically. The Pioneer 2 robotic arm is a redundant robot with five degrees of freedom. ...
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... Previous research has reported that the redundant planar series manipulator can be used to model the human arm [30,31]. Lee and Bang [30] modeled the human arm as a 3-link planar series manipulator to design the optical mouse, which can eliminate the coordinate disturbances that occur during skilled strokes. ...
... Lee and Bang [30] modeled the human arm as a 3-link planar series manipulator to design the optical mouse, which can eliminate the coordinate disturbances that occur during skilled strokes. Ghosal [31] confirmed that the human arm can be modeled as a redundant serial manipulator and that the redundancy can be obtained from the Jacobian matrix null-space. For the serial manipulator, the redundancy is essentially kinematic [32]. ...
... where U(t) is an external force and µ s , ω 0s , α s are constant parameters. Equation (31) has been used in physics, engineering, biology, and many other subjects and is one of the most studied systems in nonlinear dynamics and chaos [25]. Using the PD scheme, the external force was used as the control input. ...
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... Subsequently, the configurations of the remaining slack cables can be obtained by utilising the inverse kinematic algorithms of serial manipulators with rigid links. However, redundancy resolution techniques (see, e.g.,Ghosal, 2018) might have to be utilised depending on the number and type of joints used for connecting those rigid links. Moreover, the input slack cable's length must be greater than the Euclidean distance between its exit and anchoring points. ...
Cable-driven parallel robots manipulate the motions of a moving platform with the help of multiple cables connected to it. These robots possess lower inertias, larger workspaces and higher load-carrying capacities when compared to the conventional parallel manipulators. Accordingly, CDPRs are employed in various fields of applications, including construction, inspection, rescue operations and rehabilitation. Further details of the previous works on various research topics of CDPRs can be found in the book by Pott (2018). In the present work, simulations of the dynamics of CDPRs are performed. The inertia of cable, its stiffness and damping properties associated with deflections in the axial, transverse and lateral directions are included in the dynamic model.
A new approach to improve the computational efficiency of the forward dynamic analyses of the CDPRs is developed. With its help, a novel methodology to solve the forward kinetostatic problems of CDPRs is proposed. Its potential in identifying both
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The ability of a manipulator to compute a geometry-aware quality index for general tasks with different joint configurations is essential. Such workspace assessment is a well known and studied field in existing robotics literature, often deployed through embodied structures such as voxelized maps. Notwithstanding, existing literature solely focuses on the assessment of a single pose (end-effector), neglecting the whole-body structure and its dexterity, which allows for secondary task optimization, nullspace motion, body placement, and improved manipulability. The proposed Enhanced Dexterity Maps (EDM) aims to close these gaps using an augmented data structure. It offers a systematic analysis of disjoint flip solutions and accommodates additional performance metrics. Further analysis of EDMs through case studies highlight the limitations of existing methods and supports the need for a whole-body analysis.
The kinematic analysis of redundant serial manipulators with
$2n+1$
revolute joints (integer
$n \geq 3$
), which we call circular manipulators, is presented in this article. The structure of the kinematic chain of circular manipulators has special properties that can be seen in the Denavit–Hartenberg parameters: all orthogonal distances are zero, all even-numbered offsets are zeros, but odd-numbered offsets are not. Typical manipulators that fulfill these properties are redundant 7R serial chains (
$n=3$
) that mimic the human arm, e.g., the lightweight robot arm KUKA LBR iiwa. This 7R circular manipulator has self-motion as rotation around an axis that goes through two fixed points for a fixed pose. First, radical reparametrization is presented based on the swivel angle of the closed-form inverse kinematics solution for the 7R circular manipulator. Second, for a six-dimensional task, the inverse kinematics solution for redundant serial manipulators with
$2n+1$
revolute joints (
$n\geq 3$
) is reparametrized by the swivel angle and other
$2n-6$
rotation parameters. From a geometric point of view, for a circular manipulator with
$2n+1$
revolute joints, one can have
${n(n-1)}/{2}$
choices of such circular rotations. Third, we conjecture numerical kinematic singularities for circular manipulators in a recursive formula, confirming
$n=5,6,7$
.
A 7 degrees-of-freedom (DOF) humanoid robotic arm is proposed based on the comfort and affinity of human-robot interaction. For the characteristics of the robotic arm with end pose coupling, an integrated approach based on the analytical and reverse order methods is proposed to obtain the closed-form solution of the robotic arm at the position level. The coordinate system establishment method and mapping relationship of the Denavit-Hartenberg (D-H) parameters at positive and reverse order robotic arms are deduced. Subsequently, the analytical solution of the reverse order robotic arm is derived based on the parametrization method, and the feasible range of the arm angle is obtained using the joint limits. Additionally, the novel global arm angle optimization algorithm is proposed to simplify calculation in the intelligent algorithm, and the relationship between the optimization factors and global arm angle is analyzed. Finally, the validity of the methods is verified by the kinematics simulation based on the Robot Operating System (ROS). The simulation results demonstrate that the proposed integrated approach and global arm angle optimization algorithm can effectively solve the closed-form solution of the robotic arm.
The aim of this study is to solve the force distribution problem for a special class of musculoskeletal robot arms. The proposed method expresses a vector of actuator forces as the direct sum of three components: one produces control torque, another joint stiffness, and the other neither of them. The decomposition allows us to find the actuator force vector producing desired joint stiffness independently from the actuator force vector generating desired control torque. The ultimate goal of this research is to develop a robot arm that possesses a human-like stiffness property. To facilitate the controller design, we make the following assumptions: the robot arm consists of two links and six muscle-like actuators; the moment arms of the actuators are fixed; the force generation of the actuators is described by a special Hill-type model; the actuators can pull and push. This paper formulates the conditions for the actuator force vector space to be decomposed into the direct sum and provides a particular solution to the distribution problem. The validity of the proposed method is demonstrated by using numerical simulations.
