Robot system controlling method, robot system, and control apparatus for quadrupedal robot

A robot system comprising:

• a link whose base end is swingably supported by a fixing member;
• a pair of actuators connected to the fixing member and the link and adapted to swing the link using a difference between contraction forces;
• and
• a control apparatus adapted to adjust the contraction forces of the actuators based on respective contraction force command values and thereby control operation of the link, wherein
• the control apparatus comprises:
• a swing angle detection sensor adapted to detect a swing angle θ1 of the link with respect to the fixing member,
• a deviation calculation unit adapted to calculate a value which represents a deviation between the swing angle θ1 and a target swing angle ra,
• a torque command generating unit adapted to perform PID control calculations on the value which represents the deviation and thereby generate a torque command value T1 to swing the link,
• a multiplication unit adapted to calculate a product U1×r of length r of a moment arm from a swing center of the link and a stiffness command value U1 which represents a sum of the contraction force command values, a torque command correction unit adapted to output a new torque command value T1 whose absolute value is limited to or below the product U1×r if the absolute value of the torque command value T1 generated by the torque command generating unit is larger than the product U1×r while outputting the torque command value T1 generated by the torque command generating unit as it is if the absolute value of the torque command value T1 generated by the torque command generating unit is equal to or smaller than the product U1×r, and
• a contraction force command value calculating unit adapted to determine the contraction force command values using calculation formulae (U1+T1/r)/2, (U1−T1/r)/2 based on the torque command value T1 output from the torque command correction unit.