Method for controlling at least one servomotor, associated control device, robot and computer program product

A method for controlling at least one servomotor using a converter, the method comprising:

• obtaining a converter, the converter comprising:
• an input circuit connected to an electrical grid,
• a direct-voltage DC link operatively coupled for receiving electrical energy from the input circuit,
• a first switching device which is designed, in its switched-on state, to feed the direct-voltage DC link with electrical energy from the input circuit and, in its switched-off state, to prevent a feed of the direct-voltage DC link from the electrical grid so that no electrical energy from the electrical grid reaches the direct-voltage DC link,
• at least one inverter circuit operatively coupled for receiving electrical energy from the direct-voltage DC link and has controllable power semiconductor switches for electrically controlling the at least one servomotor, and
• a second switching device which is designed, in its switched-on state, to feed the at least one servomotor with electrical energy from the inverter circuit in order to drive the at least one servomotor and, in its switched-off state, to prevent a driving of the at least one servomotor so that no electrical energy driving the at least one servomotor goes from the inverter circuit to the servomotor;
• monitoring a circuit of the direct-voltage DC link that is connected to the input circuit for the flow of an electric current;
• switching off the first switching device in response to the occurrence of a stop signal, in order to end the supply of the direct-voltage DC link from the electrical grid;
• braking the at least one servomotor by controlling the power semiconductor switches of the inverter circuit in a generative braking operation, or via a short-circuit braking, in order to reduce the rotation speed of the at least one servomotor, in response to detecting with the monitoring that an electric current is not flowing in the circuit that connects the input circuit to the direct-voltage DC link after the first switching device has been switched off;
• and
• switching off the second switching device in order to prevent a feeding of electrical energy from the direct-voltage DC link into the at least one servomotor in response to detecting with the monitoring a flow of electric current in the circuit that connects the input circuit to the direct-voltage DC link after the first switching device has been switched off;
• wherein the converter is designed as a frequency converter, the electrical grid is an alternating-voltage grid, and the input circuit is designed as a rectifier circuit, the method further comprising:
• monitoring a circuit of the direct-voltage DC link and that is connected to the rectifier circuit for the flow of an electric current,
• switching off the first switching device in order to end the supply of the direct-voltage DC link from the alternating-voltage grid in response to the occurrence of a stop signal,
• braking the at least one servomotor by controlling the power semiconductor switches of the inverter circuit in a generative braking operation, or via a short-circuit braking, in order to reduce the rotation speed of the at least one servomotor, in response to detecting with the monitoring that an electric current is not flowing in the circuit that connects the rectifier circuit to the direct-voltage DC link after the first switching device has been switched off, and
• switching off the second switching device in order to prevent a feeding of electrical energy from the direct-voltage DC link into the at least one servomotor in response to detecting with the monitoring a flow of an electric current in the circuit that connects the rectifier circuit to the direct-voltage DC link after the first switching device has been switched off;
• wherein monitoring the circuit that connects the rectifier circuit to the direct-voltage DC link for the flow of an electric current during running operation of the frequency converter comprises monitoring during operational control of the servomotor independently of the presence of a stop signal.

A computer program product for controlling at least one servomotor using a converter, wherein the converter comprises:

• an input circuit connected to an electrical grid,
• a direct-voltage DC link operatively coupled for receiving electrical energy from the input circuit,
• a first switching device which is designed, in its switched-on state, to feed the direct-voltage DC link with electrical energy from the input circuit and, in its switched-off state, to prevent a feed of the direct-voltage DC link from the electrical grid so that no electrical energy from the electrical grid reaches the direct-voltage DC link,
• at least one inverter circuit operatively coupled for receiving electrical energy from the direct-voltage DC link and has controllable power semiconductor switches for electrically controlling the at least one servomotor, and
• a second switching device which is designed, in its switched-on state, to feed the at least one servomotor with electrical energy from the inverter circuit in order to drive the at least one servomotor and, in its switched-off state, to prevent a driving of the at least one servomotor so that no electrical energy driving the at least one servomotor goes from the inverter circuit to the servomotor;
• the computer program product comprising program code stored in a non-transient, computer-readable storage medium, the program code, when executed by a computer, causing the computer to:
• monitor a circuit of the direct-voltage DC link that is connected to the input circuit for the flow of an electric current,
• switch off the first switching device in response to the occurrence of a stop signal, in order to end the supply of the direct-voltage DC link from the electrical grid,
• brake the at least one servomotor by controlling the power semiconductor switches of the inverter circuit in a generative braking operation, or via a short-circuit braking, in order to reduce the rotation speed of the at least one servomotor, in response to detecting with the monitoring that an electric current is not flowing in the circuit that connects the input circuit to the direct-voltage DC link after the first switching device has been switched off, and
• switch off the second switching device in order to prevent a feeding of electrical energy from the direct-voltage DC link into the at least one servomotor in response to detecting with the monitoring a flow of electric current in the circuit that connects the input circuit to the direct-voltage DC link after the first switching device has been switched off.