Motor control device

A motor control device for controlling driving of a motor, which outputs torque to a load by rotation of a shaft fixed to a rotor, the motor control device comprising:

• a computer configured to determine a rotation stress abnormality indicating that a rotation stress, which is applied inversely from the load to a protection target member related to the rotation of the shaft or torque transmission to the load, is excessive based on that an absolute value of a rotation evaluation value exceeds a stress threshold value set to be larger than an upper limit value realized in normal drive control, the rotation evaluation value being an angular velocity, a rotation angular acceleration or a related value corresponding to the angular velocity or the rotation angular acceleration, wherein:
• the stress threshold value has at least two level values, which includes a short-term threshold value and one or more threshold value smaller than the short-term threshold value including a normal threshold value;
• the computer is configured to determine a short-term stress abnormality when the absolute value of the rotation evaluation value exceeds the short-term threshold value once;
• and
• the computer is configured to calculate a conversion value based on the absolute value of the rotation evaluation value when the absolute value of the rotation evaluation value exceeds the normal threshold value and determines an integrated stress abnormality when an integrated value of the conversion value exceeds a determination threshold value.