Electric-parking-brake control device and electric-parking-brake control method

An electric-parking-brake control device, for improving accuracy in computing a motor stop current irrespective of variations in motor characteristics or absence of an idling period, comprising:

• a controller that controls thrust of a piston that presses a brake pad by driving of a motor on a basis of a current of the motor and a voltage of the motor,
• wherein the controller includes a motor stop current computation unit that computes, prior to a generation of thrust sufficient to contact the brake pad, a stop current of the motor, and the motor stop current computation unit is configured to:
• in a current variation period before an idling current period, compute, as a plurality of prospective values, a plurality of candidate parameter values each representing a variation in the current and the voltage or a variation in a function including the current and the voltage in the idling current period;
• at a predetermined time during the current variation period that corresponds to a boundary point at which the current becomes substantially constant from a state in which the current varies, select one of the plurality of prospective values whose associated approximate expression most accurately reproduces a measured waveform of the current and the voltage;
• and
• on a basis of the variation in the current and the voltage or the function related to the selected prospective value, estimate at least one characteristic parameter of the motor including a torque constant, an electric resistance, or a viscosity coefficient, and compute the stop current of the motor from the at least one characteristics parameter.