Robot apparatus and control method therefor

A robot apparatus comprising:

• a robot mechanism having a plurality of joints;
• a plurality of actuators operable to drive joint axes of the robot mechanism;
• and
• a robot controller operable to drive the actuators based on a cost function that is a function of torque reference inputs for the actuators,
• wherein:
• the robot controller has a minimum-of-cost-function computation portion for calculating the minimum of the cost function, and the robot controller is operable to drive the actuators so that the value of the cost function calculated by the minimum-of-cost-function computation portion becomes minimum;
• and
• the robot apparatus further comprises position sensors operable to measure positions of the joint axes,
• wherein:
• the minimum-of-cost-function computation portion is operable to calculate as independent-axis position reference inputs the positions of the independent axes when the cost function becomes minimum;
• the robot controller further has an individual-axis feedback control portion operable to calculate independent-axis torque reference inputs such that the positions of the independent axes from the position sensors converge to the independent-axis position reference inputs calculated by the minimum-of-cost-function computation portion;
• the robot controller further has an individual-actuator weight computation portion operable to calculate individual-actuator weights that show a relative degree of importance of the plurality of actuators;
• the individual-axis feedback control portion has an independent-axis control portion operable to calculate control gains for the independent axes in proportion to the individual-actuator weights calculated by the individual-actuator weight computation portion, and, using the calculated control gains, is operable to calculate the independent-axis torque reference inputs;
• and
• the individual-actuator weight computation portion is operable to calculate an individual-actuator weight for each actuator according to a level of importance of motion of a corresponding joint axis caused by the actuator.