作者:
R.G. BonitzT.C. HsiaSystems
Control and Robotics Laboratory Department of Electrical and Computer Engineering University of California Los Angeles Davis CA USA
An internal force-based impedance control scheme for two coordinating robots manipulating a rigid object via palm grasping is introduced. The minimal internal force required to maintain the grasp on the object is comp...
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An internal force-based impedance control scheme for two coordinating robots manipulating a rigid object via palm grasping is introduced. The minimal internal force required to maintain the grasp on the object is computed from the frictional constraints and sensed forces. A closed-form solution to the minimization problem is developed which makes the algorithm suitable for real-time control. The controller uses sensed moments at the palm interface to maintain proper orientation of the palms to achieve maximum surface contact. Each manipulator's nonlinear dynamics is compensated by a robust auxiliary controller which is insensitive to robot-model uncertainty and payload variation. The controller is only weakly-dependent on each manipulator's inertia matrix. Stability of the system is analyzed. Rigorous experimental investigations are are performed and the results presented which validate the proposed concepts.
This paper proposes a method of 3-dimensional measurement of a planar surface by using two fixed light sources and a TV camera. A set of two images is recorded by the camera switching on each light alternately. The pe...
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This paper proposes a method of 3-dimensional measurement of a planar surface by using two fixed light sources and a TV camera. A set of two images is recorded by the camera switching on each light alternately. The peak of the luminance distribution in each image is detected, and the orientation and distance of the planar surface are calculated. The position of the peak of a luminance distribution can be estimated accurately by using an image processing. The light sources can be conventional apparatus with no particular structure. The method is simple and suitable for a vision system on an indoor mobile robot.
Passivity based controllers are used in structural control due to their inherent robustness properties. These controllers require sensor/actuator collocation. In this paper, we consider the design of a "squaring ...
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Passivity based controllers are used in structural control due to their inherent robustness properties. These controllers require sensor/actuator collocation. In this paper, we consider the design of a "squaring down" matrix which renders a system passive by using a linear combination of all collocated and non-collocated sensor/actuator pairs. The design uses experimental transfer functions and does not require the knowledge of the system model. The problem of finding the squaring down matrix is cast as a solution to a set of linear matrix inequalities (LMIs) subject to some additional performance considerations. The design procedure of the squaring down matrix assumes that velocity information is available from the sensors which is not generally the case. We show that the squaring down matrix can be implemented without the use of such velocity information. We provide experimental results gathered from the single link flexible beam setup in the C/sub La/MS laboratory at RPI to show that implementation of passive loops without velocity measurements provides very good results.
Smart materials such as piezoceramics and shape memory alloys (SMAs) exhibit significant hysteresis and in order to estimate the effect on open and closed loop control a suitable model is needed. One promising candida...
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Smart materials such as piezoceramics and shape memory alloys (SMAs) exhibit significant hysteresis and in order to estimate the effect on open and closed loop control a suitable model is needed. One promising candidate is the Preisach independent domain hysteresis model that is characterized by the congruent minor loop and wiping out properties. Comparable minor loop and decaying oscillation test data for a multi-sheet piezoceramic actuator (made of lead zirconate titanate) attached to a flexible beam are presented and are seen to be very consistent with the two Preisach model properties. The commanded parameter is the sheet transverse electric field while the measured parameter is an approximately colocated strain induced in the beam. Equivalent data for a Nitinol SMA wire muscle, attached to the same beam, are also presented. The input and output parameters are the SMA current and a beam strain respectfully. The minor loop and wiping out evidence is less strong than that of the piezoceramic case, but encouraging. In all experiments the quasi-steady state responses were generated in order to avoid exciting beam flexible modes which would complicate the analysis.
Utilization of inertial actuators, such as torque wheels, for vibration damping of a single-link flexible manipulator is considered. The torque wheel is mounted at the end effector of the manipulator to provide a bend...
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Utilization of inertial actuators, such as torque wheels, for vibration damping of a single-link flexible manipulator is considered. The torque wheel is mounted at the end effector of the manipulator to provide a bending moment at the tip for vibration suppression and pointing purposes. The torque exerted by the torque wheel at the end-effector of the manipulator is achieved through controlling the velocity of the torque wheel. A decentralized control scheme is advocated in this paper for slewing and vibration suppression. The local loop around the torque wheel is closed through feedback of the accelerometer signal at the tip. Experimental results are provided to show the effectiveness of the proposed method for end-effector positioning of flexible-link manipulators. Although the experimental results reported are for a single-link flexible manipulator, the results are applicable to the multi-link case. It may be shown that the dynamics from the voltage input to the torque wheel mounted at the tip to the tip position is minimum phase and hence invertible given that an inner-loop controller has been applied to stabilize the rigid-body motion.< >
In this paper, a fuzzy force control algorithm is suggested for commercialized industrial robots equipped with the position servo drives, where control rules of the proposed fuzzy controller are changed according to t...
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In this paper, a fuzzy force control algorithm is suggested for commercialized industrial robots equipped with the position servo drives, where control rules of the proposed fuzzy controller are changed according to the magnitude of environmental stiffness in such a way that good force response is maintained regardless of changes of environmental stiffness. Specifically, some fuzzy control rules are designed for several representative environmental stiffness values, and then a control action for a given arbitrary environmental stiffness value is decided by a fuzzy interpolation method. To show the validity of the proposed fuzzy controller, several experimental results are illustrated, where a 5-axis articulated robot manipulator equipped with the wrist force/torque sensor system and our prototype dual robot controller are employed.< >
The reasons for integrating collision avoiding path planning into a task-level programmable multi-sensor robot system are put forward. The underlying system architecture and the specific approaches for environment mod...
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The reasons for integrating collision avoiding path planning into a task-level programmable multi-sensor robot system are put forward. The underlying system architecture and the specific approaches for environment modelling, task planning and path planning are discussed. Task planning is performed using a rule based expert sytem and a frame representation of relevant environment data. Path planning is based on a configuration-space approach with a fast new algorithm for obstacle transformation. Results gained from experimental laboratory work are presented and show some advantages and problems of the entire system.
In this paper, an approach to modelling of a robotic assembly cell is proposed and a method for managing the cell operation is described using a knowledge base. Since the modelling structure is based on the concept of...
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In this paper, an approach to modelling of a robotic assembly cell is proposed and a method for managing the cell operation is described using a knowledge base. Since the modelling structure is based on the concept of the state variable, the relationships between states are described by the state transition map (STM). The knowledge-bases for state transition and assembly job information are obtained from the STM and the assembly job tree (AJT), respectively. Using the knowledge-base, the system structure is discussed in relation to both managing the cell operation and evaluating the performances. Finally, a simulation algorithm is presented with the simulation results to show the significance of the proposed modelling approach.
The authors attempt to achieve both high dynamic performance and maximal power efficiency for induction motors by means of linear decoupling of rotor speed (or motor torque) and rotor flux. The induction motor with th...
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The authors attempt to achieve both high dynamic performance and maximal power efficiency for induction motors by means of linear decoupling of rotor speed (or motor torque) and rotor flux. The induction motor with the proposed controller possesses the input-output dynamic characteristics of a linear system such that the rotor speed (or motor torque) and the rotor flux are decoupled. The rotor speed (or motor torque) responses are not affected by abrupt changes in the rotor flux, and vice versa. The rotor flux need not be measured but is estimated by the well-known flux simulator. The effect of large variation in the rotor resistance on the control performances is minimized by using a parameter adaptation method. The authors present simulation and experimental results as well as mathematical performance analyses.< >
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