Seiko Instruments Inc

Seiko Seiki Kabushiki Kaisha

Tsutomu Mita

Akira Shimada

Yoshinobu Ohtachi

A robot controller is provided which can smoothly switch the mode between a position control in a free space and a position or force control to a contact surface, so that even if the contact surface has an unknown geometric error, the control system mode can be switched without the damage of a contact object and a workpiece and the out-of-control of the robot. The workpiece is moved to approach an estimated contact surface within the free space under a position control. Next, a groping motion is carried out under a position control from the estimated contact surface to an actual contact surface, and switched to a contact motion under a force control at the time point when the detected force value exceeds a certain threshold value. Then, a leaving motion is carried out.

Robot controller

A location-force target path creator creates a smooth target path function from target values among values of location, position, force and moment given for a force control system. The target values are set as nodes together with times for which the target values are applied. The nodes are projected onto a time axis having a time region which is divided into a series of time regions. A target path function is calculated for an element motion by applying a boundary condition to each of the time regions.

Location-force target path creator

An interacting term existing in a control system is decoupled on the basis of a regular condition of a decoupling matrix. Then, an hyperplane &sgr; which has been obtained to satisfy the Lyapunov stability condition is designed. A control quantity is converged along the hyperplane &sgr;. In this case, even if the uncertainty is generated in a C matrix for connecting a state variable x(t) and an output y(t) of an object to be controlled, it is possible to converge the control quantity while always satisfying the Lyapunov stability condition. A non-linear input gain k,(x,t) used in the control system is designed to be greater than a predetermined value when there is no uncertainty in the C matrix to satisfy the Lyapunov stability condition. Also, a control input signal based upon the sliding mode decoupling control is converted to an articulation torque by a Jacobian. Also, for the control input signal, reverse dynamics of non-linear force are added thereto.

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Kanagawa, Japan

Tsutomu Mita