The authors consider the problem of efficient computation of the forward kinematics of a six-degree-of-freedom robot manipulator built to study autonomous assembly of parts in space. The manipulator, based on the Stew...
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The authors consider the problem of efficient computation of the forward kinematics of a six-degree-of-freedom robot manipulator built to study autonomous assembly of parts in space. The manipulator, based on the Stewart platform mechanism, consists mainly of two platforms and six linear actuators. The closed-form solution of the inverse kinematics is formulated in such a way as to optimize the computation efficiency of the iterative solution of the forward kinematics using the Newton-Raphson method. A modified Jacobian matrix which relates length velocities to Cartesian translational velocities and time rates of change of roll-pitch-yaw angles is introduced. Computer simulation is performed to evaluate the computation efficiency of the developed computation schemes.< >
The design and control of an efficient two-joint, two-link flexible arm are described. This efficient arm was designed and built to use most of the energy (provided by the motors) in performing the tasks instead of mo...
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The design and control of an efficient two-joint, two-link flexible arm are described. This efficient arm was designed and built to use most of the energy (provided by the motors) in performing the tasks instead of moving the arm structure. The arm has most of the mass concentrated at the tip and uses a special mechanical configuration to decouple radial tip motions from angular tip motions. An important problem when controlling lightweight flexible arms is the large Coulomb friction of the motors. A two-nested-loop multivariable controller is used to control the lightweight flexible arm with friction in the joints. The inner loop controls the position of the motors while the outer loop controls the tip position. The resolved acceleration method is generalized to control this flexible arm. The compliance matrix is used to model the oscillations of the structure and is included in the decoupling/linearizing term of this controller. Experimental results are presented.< >
An adaptive learning control approach is proposed which combines a mechanism to improve the control input sequence as well as to improve the learning control scheme based on the knowledge learned about the unknown sys...
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An adaptive learning control approach is proposed which combines a mechanism to improve the control input sequence as well as to improve the learning control scheme based on the knowledge learned about the unknown system and environment. The iterative learning control problem is treated from the 2D system point of view. A 2D model for a class of iterative learning control system is formulated. A learning gain estimator algorithm based on the 2D model is presented. The overall learning control system structure is given. The proposed learning control scheme does not require prior knowledge of the controlled system and has the ability to generalize the knowledge learned from one task operation to other tasks. This scheme can be applied to nonlinear system control problems. To demonstrate the feasibility of the proposed learning algorithm, simulation results on learning control for a three-water-tank system are given. The results show an excellent learning performance, even for nonrepetitive tasks.< >
An adaptive learning control approach is proposed that combines a mechanism to improve control input sequence as well as to improve the learning control scheme based on the knowledge learned about unknown system and e...
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An adaptive learning control approach is proposed that combines a mechanism to improve control input sequence as well as to improve the learning control scheme based on the knowledge learned about unknown system and environment. First, the iterative learning control problem is treated from the 2-D system point of view. A 2-D model for a class of iterative learning control systems is formulated. Then a learning gain estimator algorithm based on the 2-D model is presented. The overall learning control system structure is given.< >
All linear multirate controllers for a given multirate sampled-data system plant are parameterized in terms of a single parameter Q(z) that is allowed to be any stable transfer matrix provided that certain causality c...
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All linear multirate controllers for a given multirate sampled-data system plant are parameterized in terms of a single parameter Q(z) that is allowed to be any stable transfer matrix provided that certain causality conditions are met. The result parallels a well-known parameterization result for single-rate sampled-data plants. The parameterization suggests architectures for multirate controllers.< >
The kinematic and dynamic modelling of robot manipulators are of such computational complexity that control schemes embodying on-line calculation of the robot model have previously been impossible at an economic cost ...
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The kinematic and dynamic modelling of robot manipulators are of such computational complexity that control schemes embodying on-line calculation of the robot model have previously been impossible at an economic cost in terms of computer hardware. However, the recent development of the transputer has transformed this situation, as shown in the paper. On-line schemes using transputers are shown to be feasible as solutions for two significant computational problems in manipulator control: computing the dynamic model, and computing a time-optimal path.
Advanced control strategies require the inclusion of the dynamical model of the robot arm in the control law. However, the dynamics consist of a highly coupled and non-linear set of equations. Thus, this complexity ha...
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Advanced control strategies require the inclusion of the dynamical model of the robot arm in the control law. However, the dynamics consist of a highly coupled and non-linear set of equations. Thus, this complexity has always presented a major obstacle in real-time dynamic control applications. The computation ally efficient solution of this problem will lead to a better comprehension of the key factors effecting robot operations. This work describes a solution of this problem by employing a parallel processing approach. The dynamics are computed by using a semi-customized Newton-Euler formulation. The algorithm is distributed over a highly- coupled multiple? instruction multiple-data steram (MIMD) computer architecture. The computer system is constructed from general purpose (VLSI) building blocks called the (TRANSPUTER). The cost-effective ness and speed of the scheme is demon strated by a case study (PUMA 560 robot arm). The communication issues between the different processors and discussed. Speed-up results are included to show the superiority and advantages of the parallel approach.
An approach to intelligent PID (proportional integral derivative) control of industrial systems which is based on the application of fuzzy logic is presented. This approach assumes that one has available nominal contr...
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An approach to intelligent PID (proportional integral derivative) control of industrial systems which is based on the application of fuzzy logic is presented. This approach assumes that one has available nominal controller parameter settings through some classical tuning technique (Ziegler-Nichols, Kalman, etc.). By using an appropriate fuzzy matrix (similar to Macvicar-Whelan matrix), it is possible to determine small changes on these values during the system operation, and these lead to improved performance of the transient and steady behavior of the closed-loop system. This is achieved at the expense of some small extra computational effort, which can be very easily undertaken by a microprocessor. Several experimental results illustrate the improvements achieved.< >
It is shown that on the set of w-input, p-output asymptotically stable, minimal, nth order systems that the H∞p·mand the RNquoiient induced topologies coincide. Implications of this in frequency domain system id...
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It is shown that on the set of w-input, p-output asymptotically stable, minimal, nth order systems that the H∞p·mand the RNquoiient induced topologies coincide. Implications of this in frequency domain system identification are discussed
A special active compliance law is presented as the feedback element in a non-master/slave (i.e. symmetric) coordination strategy with explicit force distribution for robots with multiple cooperating arms. The method ...
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