Emergency Braking Trajectory Control for Manipulator in the Case of Driver Failure

Abstract

In emergency situation robot control system stops the manipulator by shutdowning drivers and activating brakes. This mode is used in all cases of equipment failure detection or while alarm bottom is pressed on control panel. Emergency braking is uncontrolled motion. As result manipulator movement deviates from program trajectory as the relations between velocities in joints differ significantly. This creates danger of collisions with objects in robot work space. The paper describes device that can be connected to control system. Connection needs insignificant changing in hardware architecture of robot control system. Device consists of controller and individual electronic schemes that are able to activate brakes of each degree of freedom regardless from other one. This feature allows to design braking trajectory by activating brakes in specific sequence and calculated delays. Mathematical solution for deviation minimization problem of braking trajectory from program one is presented. The solution is reduced to mathematical formulas which depend of the temporary velocities and values of braking decelerations in manipulator joints. The considered way of control differs from similar one described earlier by that in emergency situation drivers turn off immediately. On the first stage manipulator brakes by friction forces in gear boxes. Theoretical evaluations show that in all cases this reduces deviations from program trajectory. Additionally the new way can be used even if fault takes place at least one of drivers.