Robot apparatus and method of controlling the same, and computer program

1. A robot apparatus having a base unit, a wheel unit of an opposed-two-wheel type mounted on the base unit and having driving wheels drivable so as to face each other, and an upper-body unit provided on an upper portion of the base unit and configured by concatenating one or more joints, the robot apparatus comprising:

an opposed-two-wheel equivalent model obtained by replacement with a wheel equivalent joint representing a degree of freedom of the wheel unit with a degree of freedom of rotation and a degree of freedom of translation of the base unit and by modeling the robot apparatus as a whole as a single manipulator structure;

a robot-state observing unit observing a current state of the robot apparatus formed of an angle and an angular velocity of each of the joints of the upper-body unit and an angle and an angular velocity of the wheel unit and reflecting the current state of the robot apparatus onto the opposed-two-wheel equivalent model;

a control unit performing a control arithmetic operation for the opposed-two-wheel equivalent model;

a transforming unit transforming a part of control target values calculated by the control unit to a control target value for the wheel unit; and

a joint control unit controlling a joint-driving actuator of the wheel unit based on the control target value of the wheel unit obtained through the transformation by the transforming unit and also controlling a joint-driving actuator other than the joint-driving actuator of the wheel unit based on a control target value calculated by the control unit.

2. The robot apparatus according to claim 1 , wherein

the wheel equivalent joint has a degree of freedom of rotation in a rotating direction and a degree of freedom of translation in a back-and-forth direction of the base unit, and

the robot-state observing unit calculates a position and a posture of the base unit from the observed angle and the angular velocity of the wheel unit.

3. The robot apparatus according to claim 1 , wherein

the control unit calculates a target joint force for each of the joints of the opposed-two-wheel equivalent model of the robot apparatus, and

the transforming unit transforms a target joint force for the wheel equivalent joint to a target joint force for the wheel unit.

4. The robot apparatus according to claim 3 , wherein

the control unit calculates a virtual force acting on the opposed-two-wheel equivalent model to obtain a motion target of the robot apparatus, and transforms the virtual force to a target joint force equivalent to the virtual force.

5. The robot apparatus according to claim 1 , further comprising

operating-force detecting means for detecting an acting force in a joint driving direction in at least a part of the joints, and

the joint control unit performs a force control over the joints.

6. The robot apparatus according to claim 5 , wherein

when a target joint force, an acting force in a joint driving direction, and a joint driving speed are given, the joint control unit determines an instruction joint force to the joint-driving actuator based on an ideal response model of the joint-driving actuator defining a relation of a joint acceleration target value obtained by the joint-driving actuator ideally making a response, and performs a force control over the joints.

7. A method of controlling a robot apparatus having a base unit, a wheel unit of an opposed-two-wheel type mounted on the base unit and having driving wheels drivable so as to face each other, and an upper-body unit provided on an upper portion of the base unit and configured by concatenating one or more joints, the method comprising the steps of:

setting a motion target of the robot apparatus;

obtaining a joint value and a joint speed of each joint-driving actuator;

calculating, based on joint values of left and right wheel-driving actuators, a joint value and a joint speed of a wheel equivalent joint representing a degree of freedom of the wheel unit with a degree of freedom of rotation and a degree of freedom of translation of the base unit, and setting all joint values and joint speeds in an opposed-two-wheel equivalent model formed by replacing the wheel unit of the robot apparatus to the wheel equivalent joints;

finding a virtual force for obtaining the motion target, transforming the virtual force to a real force, and calculating an external force and a request torque for all of the joints in the opposed-two-wheel equivalent model;

transforming a request torque to the wheel equivalent joint to a request torque to the left and right driving wheels of the wheel unit; and

performing a torque control for each of the joints according to the obtained request torque.