Provided are a method and system for controlling an electric motor, and a controller. The method comprises: controlling an electric motor to operate in an open-loop manner; determining whether a rotational speed of the electric motor reaches a preset rotational speed; if so, determining whether the absolute value of an angle difference between an open-loop angle and a calculated position angle of the electric motor is greater than a preset angle; and if the absolute value of the angle difference is less than or equal to the preset angle, controlling the electric motor to operate in a closed-loop manner so as to avoid the situation where the electric motor cannot operate stably due to problems such as electric motor speed vibration caused by too large an angle difference between the open-loop angle and the position angle.

An electronic timepiece can prevent overrunning when driving a motor at a high speed. The electronic timepiece has a controller that controls a driver to an on state or an off state according to the current value detected by the current detector; a polarity changer that determines driving one step of the motor ended and changes the polarity of the drive current when the on time or off time is detected to meet a specific condition; and a drive period adjuster that sets the terminal supplying the drive current to the coil to a first state if the remaining drive step count is greater than the remaining count evaluation number, and if the remaining drive step count is less than or equal to the remaining count evaluation number, sets the terminal to a second state in which the brake force applied to the rotor is greater than in the first state.

An electronic timepiece can prevent overrunning when driving a motor at a high speed. The electronic timepiece has a controller that controls a driver to an on state or an off state according to the current value detected by the current detector; a polarity changer that determines driving one step of the motor ended and changes the polarity of the drive current when the on time or off time is detected to meet a specific condition; and a drive period adjuster that sets the terminal supplying the drive current to the coil to a first state if the remaining drive step count is greater than the remaining count evaluation number, and if the remaining drive step count is less than or equal to the remaining count evaluation number, sets the terminal to a second state in which the brake force applied to the rotor is greater than in the first state.

This document describes stepper motor drive systems. The stepper motor drive systems can be used in many different applications including, for example, to drive a stepper motor of an occluder device in association with a heart-lung machine.

According to one embodiment, there is provided a motor control device including a detection circuit, a control circuit and a drive circuit. The detection circuit detects, in a direct current motor with a first coil and second coil, a first parameter related to an induced voltage generated in the first coil and a second parameter related to an induced voltage generated in the second coil. The control circuit changes, according to a difference between the first parameter and the second parameter, at least one of a first amplitude control value of a current of the first coil and a second amplitude control value of a current of the second coil. The drive circuit drives, according to the changed amplitude control value, the first coil and the second coil, respectively.

In order to suppress high-frequency noise in micro-step driving of a stepping motor, a motor control device (100) includes an H bridge circuit (20) and control means for driving a switching element of the H bridge circuit (20) with a PWM signal and for setting a charge mode, a fast attenuation mode, or a slow attenuation mode for a motor coil. In a range from an electrical angle where the reference current value starts descending to an electrical angle of +52°, the control means switches the H bridge circuit (20) every PWM cycle to the charge mode and then to the slow attenuation mode. In a range exceeding +52° and to +90 degrees where the reference current value starts ascending, the control means switches the H bridge circuit (20) every PWM cycle to the charge mode and, if the motor current exceeds the reference current value, then the control means switches it to the fast attenuation mode and further to the slow attenuation mode.

In order to suppress high-frequency noise in micro-step driving of a stepping motor, a motor control device (100) includes an H bridge circuit (20) and control means for driving a switching element of the H bridge circuit (20) with a PWM signal and for setting a charge mode, a fast attenuation mode, or a slow attenuation mode for a motor coil. In a range from an electrical angle where the reference current value starts descending to an electrical angle of +52°, the control means switches the H bridge circuit (20) every PWM cycle to the charge mode and then to the slow attenuation mode. In a range exceeding +52° and to +90 degrees where the reference current value starts ascending, the control means switches the H bridge circuit (20) every PWM cycle to the charge mode and, if the motor current exceeds the reference current value, then the control means switches it to the fast attenuation mode and further to the slow attenuation mode.

A trolling motor assembly is provided for attachment to a watercraft. The trolling motor assembly includes a steering assembly having a stepper motor with motor current feedback to prevent stall of the stepper motor during steering of the trolling motor. The stepper motor, which rotates the shaft to which the primary trolling motor is coupled to change the direction of thrust in accordance with a steering command, is dynamically controlled utilizing motor current feedback to change the speed of the stepper motor to adapt to the load conditions on the steering assembly. The feedback control can enable operation of the stepper motor at increased RPMs under relatively low load conditions, while preventing stalls by adjusting the drive signal to decrease the speed of the stepper motor in response to increased loads.

A trolling motor assembly is provided for attachment to a watercraft. The trolling motor assembly includes a steering assembly having a stepper motor with motor current feedback to prevent stall of the stepper motor during steering of the trolling motor. The stepper motor, which rotates the shaft to which the primary trolling motor is coupled to change the direction of thrust in accordance with a steering command, is dynamically controlled utilizing motor current feedback to change the speed of the stepper motor to adapt to the load conditions on the steering assembly. The feedback control can enable operation of the stepper motor at increased RPMs under relatively low load conditions, while preventing stalls by adjusting the drive signal to decrease the speed of the stepper motor in response to increased loads.

A valve actuator (10) has a damping circuitry including a capacitive damping circuit (37), which is activated in the event of generator operation of the stepper motor (18). The damping circuitry, together with the motor winding (26), forms a resonance assembly LCR, which has the effect of stabilising and regulating rotational speed. The rotational speed of the stepper motor (18), running in generator operation, is held constant within limits, specifically without the control intervention of control circuitry. Therefore, the damping circuitry can operate even in the currentless state of the control system and is reliable regardless of external current supply. Fast closing is achieved, and excessively long post-running of the motor (18) is reliably prevented.