P.Y. Li and R. Horowitz. Passive velocity field control of mechanical manipulators. IEEE Transactions on Robotics and Automation, 15(4), August 1999.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....may not be critical. In this paper the control task that the exercise machine must satisfy will be represented by a velocity field, i.e. the assignment of a desired velocity at every position in the configuration space of the exercise machine. We will present a passive velocity field controller (Li and Horowitz, 1995) for the exercise machine that tracks a prescribed velocity field and maintains a passivity relationship between the controlled exercise machine and its user. This controller has the additional advantage that it can be implemented using passive elements such as a linear spring and a set of four ....

....and T G are respetively the tangent and cotangent bundles of the configuration manifold G, which in this case is the circle S 1 (c.f (Marsden and Ratiu, 1993) The control objective is to make the human user follow an arbitrary time varying velocity field V d : G Theta TG. As shown in (Li, 1995), it is not possible to design a static damping controller which will track an arbitrary desired velocity field V d and make the closed loop exercise control system passive with respect to the user. The basic difficulty lies on the fact that the amount of power that a static damping controller can ....

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Li, Perry Y. and Roberto Horowitz (1995). Passive velocity field control of mechanical manipulators. In: Proceedings of the 1995 IEEE International Conference on Robotics and Automation, Nagoya, Japan.

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P. Y. Li and R. Horowitz, "Passive velocity field control of mechanical manipulators," in Proc. 1995.

....and achieves passivity of the whole system by passifying the decomposed systems individually. The passivity of this control law is also based on time domain analysis extensible to general nonlinear cases. This control law, which is based on the passive velocity field control (PVFC) technique [5, 6, 7], has the following features: 1) It enables the teleoperator to be coordinated according to a prescribed linear kinematic scaling; 2) It provides for bilateral power amplification attenuation; 3) It ensures that the closed loop system is energetically passive; 4) The dynamics of the locked ....

Perry Y. Li and Roberto Horowitz. Passive velocity field control of mechanical manipulators. In IEEE Transaction on Robotics and Automation, 1999. To be appeared in August.

....the system may leave the desired contour to keep pace with the moving trajectory. the radial reduction phenomenon where the radius of the actual contour is smaller than the desired one. Fig. 1 illustrates the situation. As an alternative, it is proposed in Part I of this paper [7] and in [6] that coordination critical tasks, such as contour following, can be encoded by a time invariant velocity field on the configuration space . An appropriately designed velocity field, which defines a desired velocity for each configuration of the mechanical system, guides the system to approach ....

....energy in the system is limited to the initial energy of the system and the additional energy input from the environment. Since the physical environments with which the machine interacts are often passive themselves, stability and safety can be enhanced. For these reasons, the PVFC algorithm in [6], 7] is a good candidate for contour following applications. In order to apply PVFC to contour following, a contour encoding velocity field must first be defined. Unfortunately, for many desired contours, such a velocity field is either difficult to define or may not even exist. The latter can ....

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P. Y. Li and R. Horowitz, "Passive velocity field control of mechanical manipulators," IEEE Trans. Robot. Automat., vol. 15, pp. 751--763, Apr. 1999.

....or haptic systems, most of which also deal with linear models [3] 6] 9] 8] 7] 19] 20] 21] 11] but use frequency domain formulations that are not easy to extend to the nonlinear setting. The coordination control law in [13] based on passive velocity field control (PVFC) technique [22], 23] 24] 25] assumes only kinematic feedback, so coordination degrades in the presence of mismatched operator and environment forcing. Moreover, the apparent inertia of the teleoperator is not programmable. To remedy these problems, we propose a passive feedforward control law that enables ....

P. Y. Li and R. Horowitz. Passive velocity field control of mechanical manipulators. IEEE Transactions on Robotics and Automation, 15(4):751--763, 1999.

....example which illustrates the properties of the control law is given in Section V. Experimental results in the context of a contour following task are presented in Section VI. Concluding remarks are contained in Section VII. Most of the results contained in this paper were first presented in [11]. II. PROBLEM DEFINITION Consider a mechanical manipulator with a dimensional configuration manifold . It is subjected to controlled actuator forces and to external forces such as disturbances and contact forces. The manipulator is fully actuated so that can be arbitrarily assigned. Let denote ....

P. Y. Li and R. Horowitz, "Passive velocity field control of mechanical manipulators," in Proc. 1995.

....system are unknown. A direct adaptive control scheme is proposed which preserves the passivity of the closed loop system and ensures that the asymptotic convergence of the velocity to the direction of desired velocity field. 1 Introduction Passive velocity field control (PVFC) was developed in [1, 2, 3] with two objectives in mind: 1) to ensure that mechanical systems with strong coordination requirements are well coordinated; 2) to enhance the safety, robustness and stability of such systems when they interact mechanically with humans and other physical environments. To these ends, the ....

....environment. This can be useful in applications like machining (cutting and deburring) and machines that cooperate and interact closely with humans such as teleoperated surgical robots, and smart exercise machines. Passive Velocity Field Control laws that have these features developed in [1, 2, 3], assuming that the model of the mechanical system is known. It has been successfully applied to various applications including the control of smart exercise machines [5, 6] contour following [7, 8] and bilateral teleoperated manipulators [9] The application to robotic deburring is currently ....

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Perry Y. Li and Roberto Horowitz, "Passive velocity field control of mechanical manipulators," IEEE Trans on Robotics and Automation, vol. To appear,

....system are unknown. A direct adaptive control scheme is proposed which preserves the passivity of the closed loop system and ensures that the asymptotic convergence of the velocity to the direction of desired velocity field. 1 Introduction Passive velocity field control (PVFC) was developed in [1, 2, 3] with two objectives in mind: 1) to ensure that mechanical systems with strong coordination requirements are well coordinated; 2) to enhance the safety, robustness and stability of such systems when they interact mechanically with humans and other physical environments. To these ends, the ....

....environment. This can be useful in applications like machining (cutting and deburring) and machines that cooperate and interact closely with humans such as teleoperated surgical robots, and smart exercise machines. Passive Velocity Field Control laws that have these features developed in [1, 2, 3], assuming that the model of the mechanical system is known. It has been successfully applied to various applications including the control of smart exercise machines [5, 6] contour following [7, 8] and bilateral teleoperated manipulators [9] The application to robotic deburring is currently ....

[Article contains additional citation context not shown here]

Perry . Li and Roberto Horowitz, "Passive velocity field control of mechanical manipulators," in Proceedings of the 1995 IEEE ICRA vol. 3, pp. 2764-2770, Nagoya, Japan.

.... Address all correspondence to this author. rial removal and to ensure that a high quality finish is achieved. In this paper, we propose a new paradigm and control approach for robot contour following and force control, based on passive velocity field control (PVFC) Li and Horowitz, 1998; Li and Horowitz, 1999) developed in recent years. Figure 1. Two link direct drive deburring robot used in this research. Traditionally, the problem of controlling a robot along a contour constrained on a surface, is specified by timed trajectories of the configuration (either in the joint or end effector coordinates) ....

....passivity has the added advantage that when the deburring tool encounters large cutting force, energy in the robot system will automatically dissipate, slowing the robot down. The deburring tool will be less likely to stall or be damaged. PVFC has previously been applied to contour following (Li and Horowitz, 1999; Li and Horowitz, 1996) In (Li and Horowitz, 1996) the potential difficulty of defining a velocity field for a particular contour is overcome by the use of a time suspension technique. Experimental results and robustness analysis in (Li and Horowitz, 1999; Li and Horowitz, 1996) demonstrated ....

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Li, P. Y. and Horowitz, R. (1999). Passive velocity field control of mechanical manipulators. IEEE Transaction on Robotics and Automation, To appear in August.

....mode to the actively constrained mode takes place when the robot is near the constraint surface. 3 Inactively constrained mode When the robot is not actively being constrained and is separated from constraint surface by a finite distance, i.e. f q e, the ordinary PVFC as proposed in (Li and Horowitz, 1995; Li and Horowitz, 1999; Li and Horowitz, 1998) can be applied. We briefly review the design here. The key idea in the design of PVFC is that the controller dynamics mimic a fictitious energy storage such as a flywheel, and that energy can be exchanged conservatively between the flywheel and the ....

....derived from (9) and then by incorporating extra terms in (4) and (5) to account for possible dependence of M f on q a , an adaptive version of the PVFC can be derived (see (Li, 1999) for details) The convergence properties of the PVFC algorithm are given by the following theorem. Theorem 1 (Li and Horowitz, 1995; Li and Horowitz, 1998; Li and Horowitz, 1999) Under the PVFC described in this section, 1. The closed loop system is passive with respect to the supply rate F T e q. 2. For each a so that a g 0, the solution q a aV a q a is a stable solution when F e 0. 3. Suppose that F ....

Li, P. Y. and Horowitz, R. (1995). Passive velocity field control of mechanical manipulators. In Proceedings of the 1995 IEEE International Conf. on Robotics and Automation, volume 3, pages 2764--2770. Nagoya, Japan.

....the contour is followed is very often not very critical. In this paper, we propose a control methodology in which the coordination aspect is made explicit by specifying the task using a velocity field on the manifold related to configuration space of the robot. The passive control law proposed in [5, 6] is used so that the defined velocity field is tracked and the robot traces out the desired contour. Using this control scheme, timing along the contour can be naturally varied online by a self pacing scheme so that the tracking performance can be improved. The experimental results of the proposed ....

....position of the robot to move along the contour. However, the requirement that the robot be at a position 1 To appear in the 1996 Japan USA Symposium on Flexible Automation, Boston USA, July 1996. specified by a predetermined trajectory at each time may be an overly stringent imposition. In [5], it is proposed that tasks such as contour following be encoded by velocity fields. A velocity field (or a vector field) Vd on the configuration space G = fqg is a map Vd : G TG s.t. Vd (q) 2 TqG; 8q 2 G, where TG = f(q; q)g is the tangent space. Thus a velocity field defines a tangent ....

[Article contains additional citation context not shown here]

Li, P.Y. and Horowitz, R., "Passive Velocity Field Control of Mechanical Manipulators", In the Proceedings of the 1995 IEEE International Conf. on Robotics and Automation, p. 2764-70, vol. 3. Nagoya, Japan, April, 1995.

....some desired velocity fields, the controller must be capable of assisting the user and of injecting energy in certain portion of the exercise motion cycle, while maintaining passivity of the closed loop system. The solution proposed in this paper combines a Passive Velocity Field Controller (PVFC) [2], 3] with a nonlinear damping term. It ensures that the interaction between the exercise machine under closed loop control and the user is passive, and under the assumption that the user s Hill surface is known a priori, enables the user to execute an arbitrarily specified exercise strategy. One ....

....requirement of the exercise machine control are also formulated. In section III, we assume that the parameters for the biomechanical model are known a priori and present the design of a novel dynamic damping controller structure, utilizing the Passive Velocity Field Control (PVFC) concepts in [2], Computer T (x, dx dt) One link direct dirve robot Human User x Fig. 1. Experimental exercise machine setup. 3] This controller structure satisfies the safety requirement and at the same time enables the user to execute an arbitrarily specified exercise strategy. In section IV, the realization ....

[Article contains additional citation context not shown here]

P. Y. Li and R. Horowitz, "Passive velocity field control of mechanical manipulators," in Proceedings of the 1995 IEEE International Conf. on Robotics and Automation, vol. 3, pp. 2764-- 2770, April 1995. Nagoya, Japan.

No context found.

P.Y. Li and R. Horowitz. Passive velocity field control of mechanical manipulators. IEEE Transactions on Robotics and Automation, 15(4), August 1999.

No context found.

P.Y. Li and R. Horowitz. Passiv ev elocity field control of mechanical manipulators. IEEE Transactions on Robotics and Automation, 15(4):751--763, 1999.

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