An optimal design and control technology of a wheel motor is proposed for small electric passenger cars. The axial-flux sandwich-type disc motor is designed with a rotor embedded with neodymium-iron-boron (NdFeB) magnets and two plates of stators, and is directly mounted inside the wheel without mechanical transmission and differential gears. Sensitivity analyses are performed to choose critical design parameters, which are the most influential in design objectives, to maximize the driving torque, efficiency, rated speed, and to minimize the weight of motor under various constraints of size, materials, and power sources. The optimal driving current waveform is proven to be the same as the fundamental harmonic of the back electromotive force to produce maximum torque with least ripples. The finite-element refinement results in the motor prototype with a maximum torque over 38 kgmiddotm and a corresponding torque density of about 1.72 kgmiddotm/kg at the maximum allowable phase current of 50.25 A (rms). Two such rear driving wheels are able to drive a 600 kg passenger car to accelerate from 0 to 40 km/h in 5 s on a 15 degree incline. This dedicated wheel motor is applicable to pure or hybrid electric vehicles as a promising solution to the direct-driven electric vehicle

We propose an improved method for angular displacement estimation based on Hall-effect sensors for driving a brushless permanent-magnet (PM) motor. The control current with an angle that leads the back electromotive force is then determined to extend the speed range of the motor. Traditionally, Hall-effect signals are measured by both the capture interrupt and periodic timer interrupt functions before the angular displacement is precisely estimated with a digital signal processor. Unfortunately, the capture interrupt function is highly sensitive to external noise. The proposed method retains the periodic timer interrupt function and simplifies the estimation operation, so that the controller is robust to external disturbances. We used the improved method to adjust the phase lead angle for driving both a surface-mounted-PM motor and an interior-PM synchronous motor. Experimental results show that the improved angular displacement estimation effectively rejects noise and is 2.9 times faster than the traditional approach.

We have applied multiobjective optimal design to a brushless dc wheel motor. The resulting axial-flux permanent-magnet motor has high torque-to-weight ratio and motor efficiency and is suitable for direct-driven wheel applications. Because the disk-type wheel motor is built into the hub of the wheel, no transmission gears or mechanical differentials are necessary and overall efficiency is thereby increased and weight is reduced. The dedicated motor was modeled in magnetic circuits and designed to meet the specifications of an optimization scheme, subject to constraints such as limited space, current density, flux saturation, and driving voltage. In this paper, two different motor configurations of three and four phases are illustrated. Finite-element analyses are then carried out to obtain the electromagnetic, thermal, and modal characteristics of the motor for modification and verification of the preliminary design. The back-electromotive forces of prototypes are examined for control strategies of current driving waveforms.

This paper presents a multiobjective optimal design and an energy compensation control for the soft valve landing of an electromagnetic valve actuator in internal combustion engines. This axisymmetric and cylindrical actuator is used to achieve continuous and independent valve timing and lifting without mechanical cams, which features a hybrid magnetomotive force with permanent magnet (PM) and electromagnet, and a secondary air gap to prevent the PM irreversibly demagnetizing. The dynamics of the electromagnetic valve are modeled with an equivalent magnetic circuit, which is used to perform both sensitivity analysis and an optimal design function to satisfy multiple objectives, such as magnetic holding force, release current, and its rising time. The energy compensation control in which the positive and negative work of an armature stroke is equalized enables a zero landing velocity to be achieved. The experimental results from a prototype actuator show that the landing velocity can be greatly reduced by adjusting the duty cycle of the landing current, and the actuating power is greatly reduced after the energy compensation control is applied.

This paper proposes a design of a surface-mounted permanent magnet (SPM) motor with a magnet surface of a sinusoidal pulsewidth-modulation (SPWM) shape. The fundamental harmonic of the flux density distribution over the SPWM-shaped magnet surface is sinusoidal, which makes the back electromotive force induced in the phase winding close to sinusoidal. Slots can be cut easily into the magnet to form an SPWM-shaped surface, and less rare-earth magnet material is used if the SPWM-shaped permanent magnet (PM) is sintered or bonded in the molds. The optimal SPWM magnet shape on the SPM motor for an electric scooter is designed by maximizing the output torque and efficiency and minimizing the magnet volume and is verified by the finite-element analysis. Prototype motors are fabricated with magnets of various shapes, with or without an SPWM surface. The amount of rare-earth magnet material used in the motor with the SPWM-shaped PMs is 9.4%-13.2% less than that without the SPWM-shaped PMs, while the maximum torque is reduced by only 3%-5.4%.