Yee-Pien Yang

Optimal Design and Control of a Wheel Motor for Electric Passenger Cars

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

Design and control of axial-flux brushless DC wheel motors for electric Vehicles-part I: multiobjective optimal design and analysis

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.

Frequency adaptive control technique for rejecting periodic runout

This paper proposes a novel adaptive controller for rejecting the periodic runout of a track-following system in the compact disk drive (CDD) with dual actuators. The control objective is to attenuate adaptively the specific frequency contents of runout disturbances without amplifying its rest harmonics. This controller can be implemented in a plug-in manner to an existing feedback control system without changing the original control setup. It is applicable to both the spindle modes of constant linear and constant angular velocity for various operation speeds. The experimental results show that the novel control strategy leads to a satisfactory performance in terms of the reduction of tracking error of CDDs.

An Electric Gearshift With Ultracapacitors for the Power Train of an Electric Vehicle With a Directly Driven Wheel Motor

A novel electric gearshift with ultracapacitors is designed for the power train of a directly driven electric vehicle. The power train consists of two major subsystems: electric propulsion and energy source. The electric propulsion subsystem is composed of a dedicated wheel motor and its drive; the energy source subsystem is equipped with a stack of lead-acid batteries and ultracapacitor cells. This electric gearshift combines different parallel and serial connections of batteries, motor windings, and ultracapacitors to accommodate various driving patterns in the permissible range of speed and torque. A control core, which is realized by a field-programmable gate array, is employed to manage the energy source and direct optimal propulsion to extend the speed range of constant power, and thereby improve vehicle performance in terms of efficiency, acceleration, and driving range.

Design and control of axial-flux brushless DC wheel motors for electric Vehicles-part II: optimal current waveforms and performance test

We present dedicated designs of optimal current waveforms for disk-type axial-flux wheel motors. The four-phase dedicated wheel motor has been designed and installed directly inside the wheel of electrical vehicles without mechanical differentials and reduction gears. We performed a torque-oriented optimization to obtain the optimal current waveform subject to various constraints for the independent winding structure. We found that the best optimal waveform with maximized torque and confined ohmic loss is proportional to the magnetic flux variation in the air gap between the stator and the rotor and has the same shape as the back-electromotive force (EMF). This finding is confirmed by both theoretical and numerical analyses. As expected, the current control waveform of the back-EMF extracted by experiments renders the best performance in terms of maximum torque and motor efficiency.

Improved Angular Displacement Estimation Based on Hall-Effect Sensors for Driving a Brushless Permanent-Magnet Motor

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.

Adaptive velocity control of DC motors with Coulomb friction identification

A new dc motor control technique for the Coulomb friction compensation is proposed. The technique uses an adaptive velocity control scheme for a dc servo motor with on-line estimated parameters, including a Coulomb friction parameter, which is a combination of the Coulomb friction torque, motor time constant, moment of inertia of the motor, and sampling time of the discrete-time motor model. The estimation model used in the adaptive control process is validated off-line by a pseudo-linear regression algorithm for system parameters in a linear ARMAX model, and by adaptive Kalman filters for the Coulomb friction parameter described as pseudo-random binary sequences

A New Energy Management System of Directly-Driven Electric Vehicle with Electronic Gearshift and Regenerative Braking

This paper proposes a novel energy management system with electronic gearshift and regenerative braking to improve the gross efficiency and driving range of an electric vehicle. This electric motorcycle is driven directly by a wheel motor, which is a custom-designed disk-type axial-flux dc brushless motor. Its stator windings are grouped into four phases and are connected in parallel or serially for high or low speed ranges. The integration of windings, batteries, ultracapacitors and the core controller constitutes the energy management system, which features a natural and smooth shifting of gears and regenerative braking electronically. The control and energy management are coded in a field programmable gate array, which also functions for the calculation and display of the state of charge of batteries. The gross efficiency of this electric vehicle is improved in the driving range by 20% with respect to that without regenerative braking scheme according to the ECE47 standard of performance test. The motor-to-wheel efficiency also was above 70% at 30 km/hr with low speed gear and at 50 km/hr with high speed gear.

Multiobjective Optimal Design and Soft Landing Control of an Electromagnetic Valve Actuator for a Camless Engine

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.

Pain model and fuzzy logic patient-controlled analgesia in shock-wave lithotripsy

Pain control in conscious patients was investigated using a push-button, demand-driven supply of drugs. A fuzzy logic patient-controlled analgesia (PCA) algorithm was compared with a conventional algorithm, for alfentanil administration in extracorporeal shock-wave lithotripsy. The conventional PCA algorithm used an initial dose of 0.25 mg, a fixed infusion rate of 60 mg h−1 and a fixed bolus size of 0.2 mg with a 1 min lockout. The fuzzy logic PCA algorithm used an initial dose of 0.25 mg, a changeable infusion rate and a bolus size of 0.1 or 0.05 mg. The infusion rate was adjusted according to a look-up table that accepted the button-pressing history over the last three lockout intervals. The look-up table was designed using fuzzy logic. The bolus size was adjusted according to the button-pressing history over the past two lockout intervals. Twelve patients were treated using conventional PCA, and thirteen were treated with PCA + fuzzy logic control (FLC). PCA+FLC patients consumed 45% less drug. Also, PCA-FLC patients had a mean delivery/demand ratio of 82%, compared with 60% in conventional PCA. When the pain intensity scale was analysed, PCA+FLC patients had acceptable pain intensity at 62%, compared with 44% in conventional PCA.