Robot control with improved safety
AssigneeABB Schweiz AG
InventorIngvar Jonsson
Life of this patent
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Abstract
For controlling a robot in a safe way, a highest voltage required for a desired robot movement is calculated. A voltage level in a DC-bus is set on the basis of the highest voltage, and current is supplied to a motor at a robot axis from the DC-bus. By limiting the voltage level in the DC-bus to correspond to an actual need for a desired robot movement at each instant unnecessary fast robot movements are prevented even in the event that an inverter controlling motor currents would by mistake attempt to drive the motor faster than desired by the operator.
Claims18
A method for controlling a robot with a robot drive unit, the method comprising the steps of:
- setting with a mode selector unit a predetermined maximum voltage level;
- calculating with the robot drive unit a highest voltage required for a robot movement;
- setting with the robot drive unit a limit of a first voltage level in a DC-bus on the bases of the maximum voltage level and the highest voltage;
- and
- supplying current to a motor at a robot axis from the DC-bus so that the motor can perform the robot movement.
A robot drive unit comprising
- a mode selector unit configured to set a predetermined maximum voltage level,
- a DC-bus supplying current to a motor at a robot axis,
- characterized in that the robot drive unit further comprises a calculation unit configured to calculate a highest voltage required for a robot movement, and a voltage source setting a limit of a first voltage level in the DC-bus on the bases of the maximum voltage level and the highest voltage, the current from the DC-bus supplied to the motor to perform the robot movement.
A robot drive unit comprising:
- a DC-bus supplying current to a motor at a robot axis;
- a voltage sensor measuring a voltage from the DC-bus;
- the robot drive unit having three operation modes, each operation mode having a predetermined maximum voltage level different from those of the remaining operation modes;
- a safety module comparing the measured voltage with the maximum voltage level of a current operation mode, and actuating an emergency stop if the voltage exceeds the maximum voltage level of the current operation mode;
- a calculation unit calculating a highest voltage required for a robot movement, and setting a limit of a first voltage level in the DC-bus on the basis of the highest voltage, the current from the DC-bus supplied to the motor to perform the robot movement.
Dependencies are inferred from the claim text.