Robot and robot control method

A robot control method of controlling a robot body by a control device, the robot body comprising:

• a link that rotates around a joint that serves as an axis;
• a first string-shaped member and a second string-shaped member connected to the link and arranged in an antagonistic manner;
• and a drive unit that includes a first actuator that generates driving force for advancing and retreating the first string-shaped member and a second actuator that generates driving force for advancing and retreating the second string-shaped member, the drive unit generating torque around the joint and stiffness of the joint based on the driving force of the first actuator and the driving force of the second actuator, the robot control method comprising:
• a position control unit of the control device calculating a torque command value around the joint of the link based on angular deviation of a joint angle relative to a reference joint angle received from outside of the robot body;
• a tensional force minimum value calculation unit of the control device obtaining a natural frequency of each string-shaped member satisfying fn>fmin>fc, fmin indicating the natural frequency, fc indicating a control bandwidth of the position control unit, fn indicating a Nyquist frequency of the position control unit, and calculating a tensional force minimum value of the first string-shaped member and the second string-shaped member from a relational expression Tmin=4×L2×μ×fmin2, L indicating length of the first string-shaped member and the second string-shaped member, μ indicating linear mass density of the first and second string-shaped members, and Tmin indicating the tensional force minimum value;
• a driving force command value calculation unit of the control device calculating driving force command values of the first actuator and the second actuator by using the tensional force minimum value, the joint angle and the torque command value so that tensional force of one of the first string-shaped member and the second string-shaped member with the smaller tensional force coincides with the tensional force minimum value;
• and
• a drive control unit of the control device generating, on the first actuator and the second actuator, driving force corresponding to the driving force command values obtained by the driving force command value calculation unit.

A robot comprising:

• a first link that rotates around a first joint that serves as an axis;
• a first wire or belt and a second wire or belt coupled to the first link in an antagonistic manner;
• a drive unit having a first actuator that generates driving force for advancing and retreating the first wire or belt and a second actuator that generates driving force for advancing and retreating the second wire or belt, the drive unit generating torque around the first joint and stiffness of the first joint based on the driving force of the first actuator and the driving force of the second actuator;
• a position control unit that calculates a torque command value around the first joint based on angular deviation of a first joint angle relative to a reference first joint angle;
• a control device that controls the drive unit at a frequency within a control bandwidth such that the natural frequencies of the first and second wires or belts are greater than the control bandwidth of the control unit and the natural frequencies of the first and second wires or belts are smaller than a Nyquist frequency of the position control unit;
• and
• a driving force command value calculation unit that calculates driving force command values of the first and second actuators based on the natural frequencies of the first and second wires or belts, the first joint angle and the torque command value around the first joint.