Jun-ichi Imura

Nonholonomic control of 3 link planar manipulator with a free joint

This paper is concerned with point-to point control of a 3 link planar manipulator where the first two joints are actuated and the third revoluted joint is unactuated. This system is a special case of under-actuated manipulators, which have nonholonomic constraints. The main result of this paper is to show that this system is feedback equivalent to the chained form which is composed of twice differential equations. In addition, we propose a controller that stabilizes the system from any initial position to any desired position.

Adaptive robust control of robot manipulators-theory and experiment

In this paper, a new adaptive robust control scheme for manipulators is proposed that overcomes the drawbacks of conventional adaptive robust control methods. The proposed controller has a simple structure by exploiting the special structure of the manipulator dynamics, and achieves the specified tracking precision without any a priori information on uncertainty. Furthermore, the feedback gain of the proposed method is almost necessary and minimum for the specified precision. To verify the advantages of the method, experimental results are shown for the trajectory control of a 2-DOF direct-drive arm. >

Robust stabilization of nonlinear systems by H ∞ state feedback

Abstract This paper is concerned with robust stabilization of nonlinear systems with unstructured uncertainty via state feedback. First, a robust stability condition is given for a closed loop system which is composed of a nonlinear nominal system and an unstructured uncertainty. Second, based on the obtained robust stability condition, a sufficient condition for robust stabilization by state feedback is given in terms of the solvability of some H ∞ state feedback control.

Exponential stabilization problem of nonholonomic chained systems with specified transient response

In this paper, we propose a control method for nonholonomic systems expressed by the chained form, where the exponential convergence to the desired final state is guaranteed and the desired transient response is achieved simultaneously. Next, we propose a trajectory generation method for the chained system, which gives a systematic procedure to find a reference trajectory that passes several given points at each specified time and exponentially converges to the origin. Finally, our method is applied to control of a 4-wheeled car. In this case, to express all the state of the 4-wheeled car by the chained form, the above method is extended to the case where several coordinate frames are needed.

Robust Control of Robot Manipulators Based on Joint Torque Sensor Information

This article is concerned with robust control of robot manip ulators in the case where joint torque sensors are available. First, we derive a dynamic equation of the manipulator with joint torque sensors that explicitly expresses a nonlinear mul tivariable structure. This dynamic equation makes it possible to construct the control systems of the manipulators with joint torque sensors based on a similar method used in the conven tional case without the sensors. Second. based on this dynamic equation, we propose a robust trajectory control scheme that achieves the specified tracking accuracy in the presence of modeling error, including the modeling error of actuator sys tems. The proposed method fully exploits joint torque sensor information to compensate the uncertainty of link and load parameters. Furthermore, an illustrative simulation result is given to show the effectiveness of the proposed control method.

Bounded real Lemma of nonlinear systems and its application to H/sub /spl infin// state feedback control

This paper is concerned with H/sub /spl infin// control of nonlinear systems. First, some necessary and sufficient conditions for nonlinear systems to be internally stable and to have the L/sub 2/ gain less than a specified number /spl gamma/ are given. These conditions are reduced to the well known bounded real lemma when one restricts the systems to be linear ones. The relations between internal stability of nonlinear systems and stabilizing solutions of the Hamilton-Jacobi equation are also clarified, which are peculiar to nonlinear systems. Second, based on the above result on the L/sub 2/ gain, a sufficient condition is given for the existence of nonlinear H/sub /spl infin// state feedback control, which completely corresponds to the linear case.<<ETX>>

A Hamilton-Jacobi inequality approach to the strict H ∞ control problem of nonlinear systems

Abstract A Hamilton-Jacobi strict inequality approach is developed for the strict H8 control problem of nonlinear systems. First, a characterization of the strict bounded real condition of nonlinear systems is given by the Hamilton-Jacobi strict inequality. Next, based on the above result, some necessary and/or sufficient conditions are given for the solvability of the strict H8 control problem via state and output feedback in the case of asymptotic stability.

Robust control of robot manipulators based on joint torque sensor information

Deals with robust control of robot manipulators in the case where joint torque sensors are available. First, the authors derive a dynamic equation of the manipulator with joint torque sensors that explicitly expresses the total nonlinear multivariable structure. This dynamic equation makes it possible to construct the control system of the manipulator with joint torque sensors using the same method as in the conventional case without the sensors. Second, based on this dynamic equation, they propose a robust trajectory control scheme which achieves the specified tracking accuracy in the presence of the modeling errors including the modeling errors of actuator systems. In the proposed method, the joint torque sensor information is fully exploited to compensate the uncertainty of link and load parameters. Furthermore, an illustrative simulation result is given to show the effectiveness of the proposed control method.<<ETX>>

Global robust stabilization of nonlinear cascaded systems

A sufficient condition is given for a class of nonlinear cascaded systems to be globally stabilizable via state feedback in the presence of uncertainty. This condition does not necessarily satisfy the so-called matching condition. The authors result is an extension of former stabilization results that treated systems without uncertainty, in the sense that the uncertainty is now taken into account. In addition, it is shown that their result is effective in the global robust stabilization of a class of input-output linearizable systems.<<ETX>>

Robust stabilization of nonlinear systems by H/sub /spl infin// state feedback

This paper is concerned with robust stabilization of nonlinear systems with unstructured uncertainty via state feedback. First, a robust stability condition is given for a closed loop system which is composed of a nonlinear nominal system and an unstructured uncertainty. Second, based on the obtained robust stability condition, a sufficient condition for robust stabilization by state feedback is given in terms of the solvability of some H/sub /spl infin// state feedback control.<<ETX>>