Robot system

A robot system comprising:

• a robot, the robot having a joint axis, the joint axis being movable in a defined movable range,
• wherein, when a target position of a tip of the robot is calculated for each calculation period and a movement command for moving the joint axis of the robot is generated, it is estimated whether or not a movement command value for the joint axis in a subsequent calculation period is within the movable range,
• wherein, if the movement command value for the joint axis in the subsequent calculation period is outside the movable range, then control is performed to cause the robot to stop moving before the robot begins movement from an initial position of the tip of the robot in the subsequent calculation period toward a target position of the tip of the robot in the subsequent calculation period, and
• wherein, if the movement command value for the joint axis in the subsequent calculation period is within the movable range, then a coasting angle of the joint axis of the robot is estimated from an actual coasting angle measured in advance and from a mechanical delay time, the coasting angle being an angle for which the joint axis of the robot will coast when the robot is commanded to stop while at the target position of the tip of the robot in the subsequent calculation period due to an emergency stop during movement of the robot in accordance with a movement command for moving the tip of the robot to the target position in the subsequent calculation period, and a post-coasting predicted position of the joint axis of the robot is determined by adding the coasting angle of the joint axis to the movement command for moving the joint axis in the subsequent calculation period, the post-coasting predicted position of the joint axis being a position at which the joint axis of the robot is predicted to stop after coasting.

A manufacturing method using a robot system, comprising:

• providing a robot having a plurality of joint axes, and a safety protection barrier arranged around the robot, the robot performing an operation inside the safety protection barrier;
• providing a controller configured to determine whether or not the robot will come into contact with the safety protection barrier during the operation at a target position of the robot in a subsequent calculation period;
• and
• causing the robot to stop moving before the robot begins movement from an initial position of the robot in the subsequent calculation period toward the target position of the robot in the subsequent calculation period if the controller determines that the robot will come into contact with the safety protection barrier.

A robot system comprising:

• a robot having an arm, the arm having an axis;
• and
• a virtual safety protection barrier with which an arm-occupied region is not allowed to come into contact, the arm-occupied region including the arm of the robot,
• wherein an actual amount of coasting (θDiMAX) obtained when a robot, which holds at least a maximum load, is stopped due to an emergency stop at a maximum speed (ωiMAX) of each axis under the maximum load is measured in advance using an actual robot system and stored,
• wherein, when a target position of a tip of the robot is calculated for each calculation period and a movement command for moving the axis of the arm of the robot is generated, it is checked whether or not the arm-occupied region at a target position of the tip of the robot in a subsequent calculation period will come into contact with the virtual safety protection barrier,
• wherein, if it is determined that the arm-occupied region will come into contact with the virtual safety protection barrier, then control is performed to cause the robot to stop moving, and
• wherein, if it is determined that the arm-occupied region will not come into contact with the virtual safety protection barrier, then:
• a speed of each axis is calculated by dividing a difference between a current position and a next target position by a calculation period time;
• a variable coasting angle is calculated by multiplying the actual amount of coasting by a value obtained by dividing the speed of each axis by the maximum speed of each axis;
• an amount of fixed-delay coasting is calculated by multiplying the speed of each axis by a fixed delay time which is preset as a mechanical delay time;
• a coasting angle of each axis of the arm of the robot is estimated by adding the variable amount of coasting to the amount of fixed-delay coasting, the coasting angle being an angle for which the axis of the arm of the robot will coast when the robot is stopped due to an emergency stop during movement of the robot in accordance with a movement command for moving the tip of the robot to the target position in the subsequent calculation period;
• and
• a post-coasting predicted position of each axis of the arm of the robot is determined based on the coasting angle of each axis and an operation command of each axis in a next calculation period time,
• wherein it is estimated whether or not the arm-occupied region at the post-coasting predicted position of each axis will come into contact with the virtual safety protection barrier, and, if it is determined that the arm-occupied region will come into contact with the virtual safety protection barrier, control is performed to cause the robot to stop moving.