Designing of Manipulator Emergency Bracking Trajectory by Sequential Drivers Shutdown Method

Abstract

The problem of emergency braking security is solved by using different means of robot stopping. They include soft deceleration as well as emergency stopping with shutdown of manipulator drivers and brakes activating. This mode is used in all cases of equipment fault detection or while alarm bottom is pressed on control panel. During braking phase the manipulator motion is uncontrollable what can lead to great deviations from program trajectory. The problem of emergency breaking is complicated enough because appropriate solution should take into account that some robot sensors and drivers are invalid. The paper describes device which can be connected to robot control system. It consists of controller and individual electronic schemes that are able to turn off power supply of each degree of freedom regardless from other one. This feature allows to design braking trajectory by turning off drivers in specific sequence and calculated delays. Connection the device to control system needs insignificant changing in hardware architecture of robot control system. Mathematical solution of deviation minimization problem for braking trajectory from program one is presented. It bases on suggestion that braking forces are constant in all braking interval. If this condition take place then solution can be became as mathematical formulas which includes the temporary velocities in manipulator joints, braking acceleration and response time of brakes.
Theoretical evaluations show that in common case deviations can be reduced in a few times. Experiments on robot-manipulator confirm these conclusions. The small deviations between braking and program trajectories exclude collisions of manipulator with the objects in robot workspace.