R.E. Clark

Design optimisation of moving-magnet actuators for reciprocating electro-mechanical systems

A methodology for the design optimisation of linear moving-magnet actuators for use in reciprocating electro-mechanical systems is described. It is analysis based and accounts for the dynamic performance with due account of the system non-linearities. Predictions are validated against measurements on a prototype actuator.

Design features for enhancing the performance of electromagnetic valve actuation systems

The paper describes a type of variable air-gap reluctance actuator that offers potential for enhancing the dynamic performance of electromagnetic valve actuation systems for internal combustion engines. In both the stator and armature, the actuator incorporates design features that allow the force-displacement characteristic to be tailored to meet operational requirements. The paper demonstrates the considerable scope for varying actuator characteristics by means of detailed two- and three-dimensional finite-element modeling. The key findings from the finite-element modeling are validated by experimental measurements on a prototype actuator.

A tubular flux-switching permanent magnet machine

The paper describes a novel tubular, three-phase permanent magnet brushless machine, which combines salient features from both switched reluctance and permanent magnet machine technologies. It has no end windings and zero net radial force and offers a high power density and peak force capability, as well as the potential for low manufacturing cost. It is, therefore, eminently suitable for a variety of applications, ranging from free-piston energy converters to active vehicle suspensions.

Design, analysis and realization of a novel magnetic harmonic gear

High performance magnetic gears are competitive with mechanical gears in terms of their torque transmission capability, and they offer significant operational benefits. Various topologies of magnetic gear have been developed, the one which is described in this paper being particularly appropriate for use in applications for which a high gear ratio is required. It is the magnetic equivalent of a mechanical harmonic gear, and can transmit ripple-free torque at a torque density of up to ~110 kNm/m3 when high energy permanent magnets are employed. The paper will describe the operating principle, design and analysis of a harmonic magnetic gear, including a dual-stage configuration which enables much higher gear ratios to be achieved. Finally, the practical realization of such a magnetic gear will be described.

Direct-Drive Rotary-Linear Electromechanical Actuation System for Control of Gearshifts in Automated Transmissions

A direct-drive electromechanical actuation system has been developed which acts directly on the shift rails of either an automated manual transmission (AMT) or a dual clutch transmission (DCT) to facilitate gear selection. Direct-drive electromechanical actuation schemes offer a number of advantages over electric motor and gearbox systems in that they have reduced mechanical hysteresis, backlash and compliance, have fewer components, are more robust, and exhibit a better dynamic response. A high-force, moving-magnet linear actuator is combined with a moving-magnet rotary actuator to enable multi-axis control and, hence, enable the selection of all transmission ratios. The measured and predicted static performance of the rotary actuator, and the dynamic performance of the combined rotary- linear actuator, mounted on a gearbox test rig, are presented.

Static Performance of a Polarized Permanent-Magnet Reluctance Actuator for Internal Combustion Engine Valve Actuation

This paper describes the topology of a permanent-magnet polarized reluctance actuator that enhances the performance of electromagnetic valve actuation systems; specifically, it reduces losses during extended periods of valve closure, improves controllability, provides a degree of fail-safe operation in the event of a system fault, and reduces currents required for system initiation during cold-starting of the engine. The paper describes the basic operating mechanism of the actuator and explains the influence of various design features on its static characteristics by means of a finite-element-based design study on a representative performance specification. A prototype device has been manufactured and its static characteristics have been measured experimentally to illustrate the utility of the proposed actuator topology and the key findings from the design study.

Controllability analysis of multi objective control systems

The performance requirements stated in project specifications often comprise conflicting objectives. These objectives may further be a complex mix of steady state and dynamic performance. Control devices such as solenoid actuators are often chosen purely on steady state force characteristics, due to the difficulty of appraising the conflicting and generally non-linear nature of the performance objectives. This can have ramifications in terms not only of the actuator performance, but also in the overall controllability of the system when closed-loop control is implemented. An example automotive application examining the multi objective controllability of electronically actuated valves is presented. Multi objective evolutionary techniques are utilised to derive the optimal force-displacement characteristics and also dynamic characteristics of the desired actuator under the constraint of design performance criteria. The selected actuator is then assessed for its controllability and dynamic performance.

Tailoring force-displacement characteristics in medium-stroke linear variable reluctance actuators

The paper is concerned with the design of medium-stroke variable reluctance actuators that exploit the tangential component of force. A method of compensating for the roll-off in force as the stator and armature come into full alignment is presented, and the scope which this offers to tailor the force-displacement characteristic to meet the demands of a particular application is illustrated by means of a case study. The case study includes finite element analysis and experimental measurements on an actuator having a stroke of 8 mm and a rated force capability of 60 N.

Direct-Drive Electromechanical Linear Actuator for Shift-by-Wire Control of an Automated Transmission

Since they are potentially more efficient and simpler in construction, as well as being easier to integrate, electromechanical actuation systems are being considered as an alternative to hydraulic systems for controlling clutches and gearshifts in vehicle transmissions. A high-force, direct-drive linear electromechanical actuator has been developed which acts directly on the shift rails of either an automated manual transmission (AMT) or a dual clutch transmission (DCT) to facilitate gear selection and provide shift-by-wire functionality. It offers a number of advantages over electromechanical systems based on electric motors and gearboxes in that it reduces mechanical hysteresis, backlash and compliance, has fewer components, is more robust, and exhibits a better dynamic response

Switched Reluctance Turbo-Generator for Exhaust Gas Energy Recovery

The paper describes a comparative study of low voltage and high voltage SR machines for use in an automotive turbo-generator exhaust gas energy recovery system. Their relative merits, in terms of the total machine loss and the loss distribution, are quantified. It is shown that the requirement for an integer number of turns imposes severe restrictions on the design of the low voltage system, whereas the flexibility to employ various winding designs in the high voltage system can be exploited to advantage. A comprehensive analysis of both the winding design and the operating control angles is presented. While the magnitude of the total machine loss is relatively insensitive to the operating voltage, the copper loss at full load is significantly lower in the high voltage system. The merits of operating the system at high voltage, in terms of the thermal rating of the electric machine, are also discussed.