Der-Min Tsay

Asymmetrical inputs for minimizing residual response

An input motion design procedure for minimizing residual response and settling time of a point-to-point electro-mechanical device at high speeds is presented. It is based on the synthesis of asymmetrical S-curve motion programs with fast acceleration and slow deceleration as the input of AC servo motors to improve the kinematic and dynamic performance of the positioning device. Experimental results are presented which illustrate the effectiveness of the proposed strategy and improved performance of the positioning device as compared to cases where conventional inputs are used.

Sensorless speed control of BLDC motor using six step square wave and rotor position detection

This paper presents a brushless DC motor (BLDCM) control system that does not require Hall sensor and speed encoder for an air conditioner fan motor. Using low cost circuits, the zero-crossing points are detected to estimate the commutated timing and speed information. Hall element shortcoming can therefore be eliminated. A modified six-step square wave pattern with pulse-width modulation is developed to simplify the conventional coordinate transformations technique. To verify the proposed method, a prototype fan motor controller is constructed and tested. Experimental results show that the proposed method has high efficiency and good performance.

Single-stage Flyback converter for led driver with inductor voltage detection power factor correction

A constant current output Flyback converter with power factor correction used for LED driving is presented in this paper. The inductor voltage detection method is applied and acquired the inductor voltage to generate the control signal. Based on this design principle, the inner loop of input current shaping is eliminating, the input voltage sensing and multiplier are also not necessary. The simulation and experimental results are provided to demonstrate the effectiveness of the control scheme based on the lab prototype boards. The output load condition is set from full load to light load, and the results show that the system drives the LEDs with high power factor.

A Procedure for Measuring Planar Cam Profiles and Their Follower Motions

A procedure that can be used to inspect planar cam contours and to evaluate their follower displacement, velocity, and acceleration curves with a higher degree of accuracy, without the aid of approximating follower displacements in traditional methods, is constructed. Based on the geometric relationships at the contact point between a planar cam profile and its follower, analytical descriptions that can be utilized to determine the follower displacement curve and its derivatives are first identified. To verify the feasibility and accuracy of the proposed procedure, analytical results generated from a theoretical design are compared to those obtained by the application of the procedure. To demonstrate the effectiveness and usefulness of the developed procedure, a measuring test bed has been constructed for a practical application example. Furthermore, the results obtained by using the developed procedure with the built measuring test bed are also compared to those obtained by using a coordinate measuring machine with the proposed algorithms.

Globoidal cam indexing servo drive control by IVSMFC with load torque estimator

This paper introduces an integral variable-structure model-following control (IVSMFC) incorporated with a load torque estimator based on variable-structure technique for a globoidal cam indexing system. IVSMFC features excellent robustness and performance properties under certain disturbances and parameter variations. However, heavy time-varying load may influence expected performance. In a cam system, when it is in motion, the load produced by inertia forces deflects the driving motor speed and, as a result, degrades the indexing precision. To fulfill the constant driving speed assumption, a load torque estimator is employed and fed forward to compensate the load torque variations. A digital-signal-processor-based globoidal cam indexing servo drive is presented and the experimental results show the effectiveness of the proposed scheme.

Single-stage Buck type LED lighting driver with new design of current integral control

This paper presents a newly designed current integral control strategy for a single-stage Buck-type LED lighting driver. The proposed system requires neither analog multipliers with traditional power factor correction circuits nor sensing input voltage to make the power factor and constant current output reachable. The design concepts are to make the impedance of line input end similar effect of an equivalent resistance. The design principle is presented separately through IsSpice simulation software and practical circuits for experiment. The measured results show that the proposed control strategy can save considerable circuit cost, and make constant current output and high power factor reachable.

Kinematical Analysis of a Novel Transmission Mechanism With Steady-Speed Output for Variable Speed Wind Turbines

For the usage in variable speed wind turbines, a novel transmission mechanism with steady-speed output is proposed in this study. The proposed mechanism, named as independently controllable transmission (ICT), can produce a required angular velocity at the output shaft, which is independently manipulated by a controller and does not depend on the angular velocity of the input shaft. By applying the ICT mechanism to the variable speed wind power systems, the turbine fluctuation can be overcome and a constant speed can be provided for the input shaft of the generator. The ICT mechanism is fundamentally composed of two sets of planetary gear trains and two sets of transmission-connecting members. Four prototypes of the ICT mechanisms are installed to experiment their kinematical characteristics and to demonstrate their feasibility of engineering application.Copyright

Generation of Globoidal Cam Surfaces With Conical Roller-Followers

Without solving any nonlinear contact equations usually encountered in traditional approaches, a relative simple, yet useful procedure to the profile determination of a globoidal cam with a conical roller-follower turret is presented. From the machining point of view for such a spatial cam cut by a conical milling/grinding tool by following its angular roller-follower turret motion, the surface geometry of the cam can be represented as the swept surfaces of the tool paths of the used cutter with a size equal to the conical roller-follower of the cam. To determine the swept surfaces of the conical tool paths, the pitch surface generated by the locus of the tool center is first identified. Subsequently, to locate the swept surfaces for the cam surfaces, the meshing vectors and meshing angles are then defined based on the pitch surface. To verify the feasibility and accuracy of the proposed procedure, both analytical formulations and numerical results are shown and compared to those obtained by an earlier technique based on the theory of screws.Copyright

Sensor-less pseudo-sinusoidal drive for a permanent-magnet brushless ac motor

The precise rotor-position information is required for a permanent-magnet brushless ac motor (BLACM) drive. In the conventional sinusoidal drive method, either an encoder or a resolver is usually employed. For position sensor-less vector control schemes, the rotor flux estimation and torque components are obtained by complicated coordinate transformations. These computational intensive methods are susceptible to current distortions and parameter variations. To simplify the method complexity, this work presents a sensor-less pseudo-sinusoidal drive scheme with speed control for a three-phase BLACM. Based on the sinusoidal drive scheme, a floating period of each phase current is inserted for back electromotive force detection. The zero-crossing point is determined directly by the proposed scheme, and the rotor magnetic position and rotor speed can be estimated simultaneously. Several experiments for various active angle periods are undertaken. Furthermore, a current feedback control is included to minimize ...

Development of a Measuring System for Planar Cam Profiles and Their Follower Motions

A measuring system that can be used to inspect planar cam contours and to evaluate their follower displacement, velocity, and acceleration curves with a higher degree of accuracy without the aid of approximating follower displacements in traditional methods is constructed. Based on the geometric relationships at the contact point between a planar cam profile and its follower, analytical descriptions that can be utilized to determine the follower displacement curve and its derivatives are first identified. To verify the feasibility and accuracy of the algorithms proposed for the measuring system, analytical results generated from a theoretical design are compared to those obtained by the application of the computing procedure. To demonstrate the effectiveness and usefulness of the developed procedure, a measuring test bed has been constructed for a practical application example. Furthermore, the results obtained by using the built measuring system are also compared to those obtained by using a coordinate measuring machine (CMM) with the proposed algorithms.Copyright