A drive system includes an electric motor and a converter that feeds the electric motor. A cable electrically connects the electric motor to the converter and has first electrical lines, a second electrical line, and third electrical lines. A voltage detection device arranged on the first cable end detects a voltage present between the second electrical line and a further electrical line, e.g., a measuring line. The further electrical line is one of the first electrical lines or one of the third electrical lines, and the further electrical line is electrically connected to the second electrical line on the second cable end. The current flowing through the further electrical line is detected by a current detection device, and a resistance value is determined from the detected voltage and the detected current and is provided to a control unit of the converter.

A wrist mechanism includes a first rotation unit, a second rotation unit, a first brake pad, and a first brake plate. The first rotation unit includes a first motor, a first rotating shaft that is connected to the first motor, and a first encoder. The first motor is operable to drive the first rotating shaft to rotate about a first axis. The first encoder measures an angle of rotation of the first rotating shaft. The second rotation unit is co-rotatable with the first rotating shaft about the first axis. The first brake pad is connected to the first rotating shaft. The first brake plate is operable to move relative to the first brake pad along the first axis. When the first brake plate is urged to move along the first axis to abut against the first brake pad, the rotation of the first rotating shaft is stopped.