Semi-closed control or fully closed control is selected as a control system for a joint using a motor configured to drive a joint of a robot arm via a reduction gear, an input-side encoder, and an output-side encoder, the semi-closed control being control in which an output of the input-side encoder is used, the fully closed control being control in which an output of the output-side encoder is used. A test run is performed plural times in which the robot arm is caused to perform a specific operation while semi-closed control is being performed on the joint, and semi-closed control or fully closed control is selected using outputs of the output-side encoder obtained in the test runs or in accordance with the content of a task that the robot arm is to be caused to perform.

A robot joint space point-to-point movement trajectory planning method. Joint space trajectory planning is performed according to the displacement of a robot from a start point to a target point during PTP movement and a limitation condition of a preset movement parameter physical quantity of each axis in a robot control system. An n-dimensional space is constructed by taking each axis of the robot as a vector, wherein n≥2, and the movement parameter physical quantity of each axis of the robot is verified according to a vector relationship between the n axes of the robot, so that a trajectory planning curve of each axis of the robot satisfies the limitation condition of the preset movement parameter physical quantity. The method has a small amount of calculations and strong real-time performance, the movement curves are mild, the control time is optimal, and the algorithm execution effect is good.

A system for distributed multi-axis motion control includes a controller having a memory configured to store a control program and a processor configured to execute the control program. A desired motion trajectory is determined for a multi-axis system having multiple axes, and an axis command is generated for each of the axes as a function of the desired motion trajectory. The system also includes multiple motors and multiple motor drives. Each of the motors corresponds to one axis for the multi-axis system, and each of the motor drives controls at least one of the motors responsive to receiving the axis command for the corresponding motor. Each of the motor drives also determines a motion state for a link driven by the motor as a function of the axis command and transmits at least a portion of the motion state to another motor drive controlling another axis.

A robot joint space point-to-point movement trajectory planning method. Joint space trajectory planning is performed according to the displacement of a robot from a start point to a target point during PTP movement and a limitation condition of a preset movement parameter physical quantity of each axis in a robot control system. An n-dimensional space is constructed by taking each axis of the robot as a vector, wherein n 2, and the movement parameter physical quantity of each axis of the robot is verified according to a vector relationship between the n axes of the robot, so that a trajectory planning curve of each axis of the robot satisfies the limitation condition of the preset movement parameter physical quantity. The method has a small amount of calculations and strong real-time performance, the movement curves are mild, the control time is optimal, and the algorithm execution effect is good.

A controlling unit obtains an error in position and orientation of each joint of a robot. The controlling unit uses an error component in a driving direction of an actuator included in the error in position and orientation u.sub.i of the joint to obtain a first correction quantity, to obtain a residual error excluding the error component in the driving direction of the actuator from the error in position and orientation of the joint, and to obtainan error in position and orientation of the end point of the robot based on the residual error of each joint. The controlling unit uses the error in position and orientation of the joint based on the error in position and orientation of the end point of the robot to obtain a second correction quantity q.sub.i, and uses the first correction quantity and the second correction quantity to correct a joint instruction value.

A system for distributed multi-axis motion control includes a controller having a memory configured to store a control program and a processor configured to execute the control program. A desired motion trajectory is determined for a multi-axis system having multiple axes, and an axis command is generated for each of the axes as a function of the desired motion trajectory. The system also includes multiple motors and multiple motor drives. Each of the motors corresponds to one axis for the multi-axis system, and each of the motor drives controls at least one of the motors responsive to receiving the axis command for the corresponding motor. Each of the motor drives also determines a motion state for a link driven by the motor as a function of the axis command and transmits at least a portion of the motion state to another motor drive controlling another axis.

A robot-position detecting device includes: a position-data acquiring unit that acquires position data indicating actual positions of a robot; a position-data input unit that receives the position data output from the position-data acquiring unit; and a position calculating unit that calculates a computational position of the robot through linear interpolation using first and second position data input to the position-data input unit at different times.