Systems and hybrid position force control processes of an industrial robot

A control process for an industrial robot, the industrial robot comprising:

• a multi-axis robot arm comprising at least two electric actuators each configured to move one part of the multi-axis robot arm with respect to another part of the multi-axis robot arm about or along an axis of movement, each electric actuator being associated with a sensor configured for measuring an articular position of the associated electric actuator,
• a robot control system comprising an axis controller module configured for calculating control setpoints of power units which deliver an appropriate electric current to the electric actuators according to an articular force setpoint and a calculation module configured for determining articular force setpoints for the axis controller module, the calculation module being coupled to the axis controller module,
• wherein the control process comprises:
• calculating a composite setpoint, the composite setpoint being time-dependent and defining articular forces and/or velocities, according to a target trajectory and to an operating mode,
• calculating a behavior matrix which describes a desired behavior of the multi-axis robot arm, the behavior matrix defining directions along which the calculated composite setpoint is to be applied, the behavior matrix being expressed in articular space,
• calculating an articular force setpoint for controlling the axis controller module and calculating a time derivative of an internal state, the internal state corresponding to an articular position and being distinct from the measured articular positions,
• command the multi-axis robot arm using the articular force setpoint,
• wherein the calculation of the articular force setpoint for controlling the axis controller module and said calculation of the time derivative each being a function of:
• the composite setpoint, the behavior matrix, the measured articular positions, articular velocities derived from the measured articular positions, and a previous internal state previously calculated in a preceding calculation cycle,
• wherein the articular force setpoint for controlling the axis controller module is calculated by applying a control function which adjusts a difference between the articular position and the internal state, the internal state being determined by integration of said time derivative of the internal state.