Impedance Control: An Approach to Manipulation
06 Jun 1984-Iss: 21, pp 304-313
TL;DR: In this paper, a unified approach to kinematically constrained motion, dynamic interaction, target acquisition and obstacle avoidance is presented, which results in a unified control of manipulator behaviour.
Abstract: Manipulation fundamentally requires a manipulator to be mechanically coupled to the object being manipulated. A consideration of the physical constraints imposed by dynamic interaction shows that control of a vector quantity such as position or force is inadequate and that control of the manipulator impedance is also necessary. Techniques for control of manipulator behaviour are presented which result in a unified approach to kinematically constrained motion, dynamic interaction, target acquisition and obstacle avoidance.
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TL;DR: This paper reformulated the manipulator con trol problem as direct control of manipulator motion in operational space—the space in which the task is originally described—rather than as control of the task's corresponding joint space motion obtained only after geometric and geometric transformation.
Abstract: This paper presents a unique real-time obstacle avoidance approach for manipulators and mobile robots based on the artificial potential field concept. Collision avoidance, tradi tionally considered a high level planning problem, can be effectively distributed between different levels of control, al lowing real-time robot operations in a complex environment. This method has been extended to moving obstacles by using a time-varying artificial patential field. We have applied this obstacle avoidance scheme to robot arm mechanisms and have used a new approach to the general problem of real-time manipulator control. We reformulated the manipulator con trol problem as direct control of manipulator motion in oper ational space—the space in which the task is originally described—rather than as control of the task's corresponding joint space motion obtained only after geometric and kine matic transformation. Outside the obstacles' regions of influ ence, we caused the end effector to move in a straight line with an...
6,515 citations
Book•
01 Jul 1990
TL;DR: This paper reformulated the manipulator control problem as direct control of manipulator motion in operational space-the space in which the task is originally described-rather than as control of the task's corresponding joint space motion obtained only after geometric and kinematic transformation.
Abstract: This paper presents a unique real-time obstacle avoidance approach for manipulators and mobile robots based on the artificial potential field concept. Collision avoidance, tradi tionally considered a high level planning problem, can be effectively distributed between different levels of control, al lowing real-time robot operations in a complex environment. This method has been extended to moving obstacles by using a time-varying artificial patential field. We have applied this obstacle avoidance scheme to robot arm mechanisms and have used a new approach to the general problem of real-time manipulator control. We reformulated the manipulator con trol problem as direct control of manipulator motion in oper ational space—the space in which the task is originally described—rather than as control of the task's corresponding joint space motion obtained only after geometric and kine matic transformation. Outside the obstacles' regions of influ ence, we caused the end effector to move in a straight line with an...
3,063 citations
Cites background from "Impedance Control: An Approach to M..."
...The potential field concept is indeed an attractive approach to the collision avoidance problem and much research has recently been focused on its applications to robot control (Kuntze and Schill 1982; Hogan 1984; Krogh 1984)....
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05 Aug 1995
TL;DR: It is proposed that for natural tasks, zero motion force bandwidth isn't everything, and incorporating series elasticity as a purposeful element within the actuator is a good idea.
Abstract: It is traditional to make the interface between an actuator and its load as stiff as possible. Despite this tradition, reducing interface stiffness offers a number of advantages, including greater shock tolerance, lower reflected inertia, more accurate and stable force control, less inadvertent damage to the environment, and the capacity for energy storage. As a trade-off, reducing interface stiffness also lowers zero motion force bandwidth. In this paper, the authors propose that for natural tasks, zero motion force bandwidth isn't everything, and incorporating series elasticity as a purposeful element within the actuator is a good idea. The authors use the term elasticity instead of compliance to indicate the presence of a passive mechanical spring in the actuator. After a discussion of the trade-offs inherent in series elastic actuators, the authors present a control system for their use under general force or impedance control. The authors conclude with test results from a revolute series-elastic actuator meant for the arms of the MIT humanoid robot Cog and for a small planetary rover.
2,309 citations
01 Mar 1998
TL;DR: Evidence is presented that robot-aided therapy does not have adverse effects, that patients tolerate the procedure, and that peripheral manipulation of the impaired limb may influence brain recovery, and one approach using kinematic data in a robot- aided assessment procedure.
Abstract: The authors' 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 the authors' approach to analyze kinematic data collected in the robot-aided assessment procedure. In particular, they 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. The authors also present one approach using kinematic data in a robot-aided assessment procedure.
1,346 citations
Cites methods from "Impedance Control: An Approach to M..."
...This is achieved using impedance control, a key feature of the robot control system [20]....
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TL;DR: In this article, a physically motivated, passivity-based formalism is used to provide energy conservation and stability guarantees in the presence of transmission delays, and an adaptive tracking controller is incorporated for the control of the remote robotic system and can be used to simplify, transform or enhance the remote dynamics perceived by the operator.
Abstract: A study is made of how the existence of transmission time delays affects the application of advanced robot control schemes to effective force-reflecting telerobotic systems. This application best exploits the presence of the human operator while making full use of available robot control technology and computing power. A physically motivated, passivity-based formalism is used to provide energy conservation and stability guarantees in the presence of transmission delays. The notion of wave variable is utilized to characterize time-delay systems and leads to a configuration for force-reflecting teleoperation. The effectiveness of the approach is demonstrated experimentally. Within the same framework, an adaptive tracking controller is incorporated for the control of the remote robotic system and can be used to simplify, transform, or enhance the remote dynamics perceived by the operator. >
1,286 citations
References
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01 Jun 1981
TL;DR: A theory of force control based on formal models of the manipulator and the task geometry is presented, isolating the programmer from the fundamental complexity of low-level manipulator control.
Abstract: Compliant motion of a manipulator occurs when the manipulator position is constrained by the task geometry. Compliant motion may be produced either by a passive mechanical compliance built in to the manipulator, or by an active compliance implemented in the control servo loop. The second method, called force control, is the subject of this paper. In particular a theory of force control based on formal models of the manipulator and the task geometry is presented. The ideal effector is used to model the manipulator, the ideal surface is used to model the task geometry, and the goal trajectory is used to model the desired behavior of the manipulator. Models are also defined for position control and force control, providing a precise semantics for compliant motion primitives in manipulation programming languages. The formalism serves as a simple interface between the manipulator and the programmer, isolating the programmer from the fundamental complexity of low-level manipulator control. A method of automatically synthesizing a restricted class of manipulator programs based on the formal models of task and goal trajectory is also provided by the formalism.
1,574 citations
TL;DR: The kinematics of remote manipulators and human prostheses is analyzed and suggests solutions to problems of coordination, motion under task constraints, and appreciation of forces encountered by the controlled hand.
Abstract: The kinematics of remote manipulators and human prostheses is analyzed for the purpose of deriving resolved motion rate control. That is, the operator is enabled to call for the desired hand motion directly along axes relevant to the task environment. The approach suggests solutions to problems of coordination, motion under task constraints, and appreciation of forces encountered by the controlled hand.
1,464 citations
TL;DR: In this article, the authors present a technique which adopts the idea of "inverse problem" and extends the results of "resolved-motion-rate" controls, which deals directly with the position and orientation of the hand.
Abstract: Position control of a manipulator involves the practical problem of solving for the correct input torques to apply to the joints for a set of specified positions, velocities, and accelerations. Since the manipulator is a nonlinear system whose joints are highly coupled, it is very difficult to control. This paper presents a technique which adopts the idea of "inverse problem" and extends the results of "resolved-motion-rate" controls. The method deals directly with the position and orientation of the hand. It differs from others in that accelerations are specified and that all the feedback control is done at the hand level. The control algorithm is shown to be asymptotically convergent. A PDP 11/45 computer is used as part of a controller which computes the input torques/forces at each sampling period for the control system using the Newton-Euler formulation of equations of motion. The program is written in floating point assembly language, and has an average execution time of less than 11.5 ms for a Stanford manipulator. This makes a sampling frequency of 87 Hz possible. The controller is verified by an example which includes a simulated manipulator.
1,231 citations
01 Dec 1980
TL;DR: In this article, a method of actively controlling the apparent stiffness of a manipulator end effecter is presented, which allows the programmer to specify the three transnational and three rotational stiffness properties of a frame located arbitrarily in hand coordinates.
Abstract: A method of actively controlling the apparent stiffness of a manipulator end effecter is presented. The approach allows the programmer to specify the three transnational and three rotational stiffness of a frame located arbitrarily in hand coordinates. Control of the nominal position of the hand then permits simultaneous position and force control. Stiffness may be changed under program control to match varying task requirements. A rapid servo algorithm is made possible by transformation of the problem into joint space at run time. Applications examples are given.
1,212 citations
"Impedance Control: An Approach to M..." refers background in this paper
...... sufficiently largeseparations between the end-effector andobjects intheenvironment (see figure2b).Thisisprecisely thetypeof non-invertible, nonl inearforce/displacement behaviour forwhichnoinverse compliance form exists.Theconcept oftuning theend-point stiffness anddamping ofamanipulator hasbeen discussed intheliterature underthegeneral heading of"compliance"', "compliant motion control", "finemotioncontrol", or ......
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01 Oct 1981
TL;DR: The class of problems that involve finding where to place or how to move a solid object in the presence of obstacles is discussed and a method of computing an explicit representation of the manipulator configurations that would bring about a collision is discussed.
Abstract: The class of problems that involve finding where to place or how to move a solid object in the presence of obstacles is discussed. The solution to this class of problems is essential to the automatic planning of manipulator transfer movements, i.e., the motions to grasp a part and place it at some destination. For example, planning transfer movements requires the ability to plan paths for the manipulator that avoid collisions with objects in the workspace and the ability to choose safe grasp points on objects. The approach to these problems described here is based on a method of computing an explicit representation of the manipulator configurations that would bring about a collision.
763 citations