Industrial robot

An industrial robot including an arm mechanism for producing movement of an operating member in a plurality of mutually perpendicular directions, drive means for driving said arm mechanism for movement of said operating member in respective ones of said directions, position sensing means for sensing amounts of displacement of said operating member, and a control apparatus for controlling said drive means to move said operating member, and characterized in that said control apparatus includes changeover means operable for selectively establishing a position control mode and a force control mode for controlling movement of said operating member, and in that during operation in said position control mode said operating member is driven to a predetermined position corresponding to a position control signal produced by said control apparatus, while during operation in said force control mode said operating member is driven from said predetermined position in a fixed direction until said control apparatus detects a cessation of movement of said operating member resulting from contact with a workpiece, said cessation of movement being detected by said control apparatus as a cessation of change in an output signal from said position sensing means, with a predetermined level of drive current supplied to said drive means following said cessation of movement, said current level being determined by a force control signal, wherein said drive means comprises a plurality of drive sections for driving said operating member in respective ones of said mutually perpendicular directions, and further comprising velocity sensing means for sensing a velocity of said operating member and current sensing means for sensing levels of drive current applied to said drive means, and in which during operation in said position control mode said control apparatus establishes for each of said drive sections a position control loop for controlling drive power applied to said each drive section in accordance with an error between a corresponding position control signal and an output signal from said position sensing means, a velocity control loop for controlling said drive power utilizing an output signal from said velocity sensing means as a feedback signal, and in which during operation in said force control mode said control apparatus establishes, for one of said drive sections which is currently selected to be actuated, a force control loop for controlling drive power applied to said one drive section in accordance with an error between a corresponding force control signal and an output signal from said velocity sensing means, and establishes a current control loop for controlling said drive power utilizing an output signal from said current sensing means as a feedback signal.