Downhole tractor control systems and methods to adjust a load of a downhole motor

A method to adjust a load of a downhole motor, the method comprising:

• receiving a user input of a desired speed and torque for a plurality of motors powering rotation of wheels of a downhole tractor;
• determining a minimum actual motor speed of the plurality of motors;
• for at least one of the plurality of motors:
• determining a power controller output based on the desired speed to control voltage of the at least one motor;
• determining a torque error based on the desired torque and a feedback torque of the at least one motor;
• determining a torque controller output based on the desired torque to control voltage of the at least one motor and the torque error;
• and
• adjusting a voltage source invertor based on a lesser of the power controller output and the torque controller output to modulate voltage provided to the at least one motor.

A downhole tractor control system, comprising:

• a storage medium;
• and
• one or more processors operable to:
• receive a user input of a desired speed and a desired torque for a plurality of motors, the plurality of motors powering rotation of wheels of the downhole tractor;
• determine a minimum actual motor speed of the plurality of motors;
• for at least one motor of the plurality of motors:
• determine a power controller output based on the desired speed to control voltage of the at least one motor;
• determine a torque error based on the desired torque and a feedback torque of the at least one motor;
• determine a torque controller output based on the desired torque to control voltage of the at least one motor and the torque error;
• and
• adjust a voltage source invertor based on a lesser value of the power controller output and the torque controller output.

A non-transitory machine-readable medium comprising instructions stored therein, which when executed by one or more processors, cause the one or more processors to perform operations comprising:

• receiving a user input of a desired speed and a desired torque for a motor that powers rotation of a wheel of a downhole tractor;
• determining an actual speed of the motor;
• determining a power controller output of the motor based on the desired speed to control voltage of the at least one motor;
• determining a torque error based on the desired torque and a feedback torque of the at least one motor;
• determining a torque controller output of the motor based on the desired torque to control voltage of the motor and the torque error;
• and
• adjusting a voltage source invertor based on a lesser of the power controller output and the torque controller output to modulate voltage provided to the motor.