Electric vehicle motors and drive control





  • Systems integration and optimisation
  • Electrical machines and drives
  • Control
  • Energy management systems
  • Energy storage systems
  • Vehicle 2 grid systems
The EMD Research Group Electric Formula 3000 car on the test track

My first exposure to electric vehicles and associated systems came back in the early 1990s when I started working in the Electrical Machines and Drives Research Group at the University of Sheffield.  EMD was the biggest group of its kind, and the opportunity to get involved with everything which was new and ground breaking seemed to be behind virtually every lab door.

EMD Research Group F3000 in hub traction motor

We had already created our first spin-out company MST- Magnetic Systems Technology, with whom I eventually carried out my PhD research as part of an Industrial CASE Award. The prototype MST in-hub traction machines can be seen in the picture above of our Formula 3000 car. The power inverter and hub motors were all sharing a common coolant system.

The original Bluebird Electric land speed record car in the EMD labs

Following on from the F3000 vehicle, the group collaborated with Sir Malcolm Campbell’s grandson Don Wales to set a new UK electric land speed record at Pendine Sands, in Carmarthenshire.

  • Stewart P. and Kadirkamanathan V., “Dynamic model reference PI control of flux weakened permanent magnet AC motor drives” IFAC Journal of Control Engineering Practice. Vol. 9, no. 11, pp.1255-1263. November 2001.
  • Stewart P., “Torque maximisation of the PMAC motor for high speed, low inertia operation” Asian Journal of Control. Vol. 5, No. 1, pp.58-64, May 2003.
  • Stewart P. and Kadirkamanathan V., “Commutation of permanent magnet synchronous AC motors for military and traction applications” IEEE Transactions on Industrial Electronics. Vol.50, No.3, pp. 629-631, June 2003.
  • Stewart P. and Kadirkamanathan V., “Dynamic model tracking design for low inertia, high speed permanent magnet AC motors”Institute of Instrumentation, Systems and Automation Transactions, vol.43, no.1, pp. 111-122, January 2004.
  • Gladwin D., Stewart P., Stewart J. and Cowley C., “DC Voltage Stabilisation For The Series Hybrid Electric Vehicle” Transactions of the Institute of Instrumentation, Systems and Automation, Vol 47/2 pp 222-228, April 2008.
  • Wilson D, Stewart P., Jewell G, Taylor B, “Methods of resistance estimation in permanent magnet synchronous motors for real-time thermal management.” IEEE Transactions on Energy Conversion Vol.25, No.3. pp. 698-707, 2010
  • Kan Liu, Q. Zhang, Z.Q. Zhu, J. Zhang, A.W. Shen, Stewart P., “Two Novel MRAS Strategies for Identification of Parameters in Permanent Magnet Synchronous Motors ”, International Journal of Automation and Computing. Vol. 7, No. 4, pp. 526-524, November 2010.
  • Wilson S., Stewart P. and Stewart J.,  “Real-time thermal management of permanent magnet synchronous motors by resistance estimation” IET Transactions in Electric Power Applications.  (9). pp. 716-726. ISSN 1751-8660, 2012.
  • Stewart P. and Kadirkamanathan V., “On the steady state and dynamic performance of model reference control for a permanent magnet synchronous motor” UKACC International Conference on Control 98. University of Wales, Swansea UK. vol.455, pp.664-669, 1-4 September, 1998.
  • Stewart P. and Kadirkamanathan V., “Dynamic control of permanent magnet synchronous motors in automotive drive applications” 1999 IEEE  American Control Conference, San Diego, USA. pp.1677-1681, June 2-4, 1999.
  • Stewart P. and Kadirkamanathan V., “Model reference PI control of a multivariable system with saturation – a case study” IFAC Workshop on Digital Control – PID 2000, Terrassa, Spain. pp.547-552, April 5-7, 2000.
  • Stewart P. and Kadirkamanathan V., “Dynamic model reference control of a PMAC motor for automotive traction drives” UKACC International Conference on Control 2000, Cambridge UK. CDRom 073.PDF. September 4-7, 2000.
  • Stewart P. and Kadirkamanathan V., “Position estimation for the PMAC motor in automotive drive applications” UKACC International Conference on Control 2000, Cambridge UK. CDRom 252.PDF. September 4-7, 2000.
  • S. D. Wilson, G. W. Jewell and P. Stewart, “ Resistance Estimation for Temperature Determination in PMSMs through Signal Injection” International Electric Machines and Drives Conference May 15-18, 2005, San Antonio, TX
  • Stewart P., Gladwin D., Stewart J. and Cowley R., “Generator voltage stabilisation for the series-hybrid vehicle”, 33rd Annual Conference of the IEEE Industrial Electronics Society (IECON 2007), Taipei, Taiwan, 5-8th November 2007. (Invited Paper)

My PhD ‘Optimal Model Reference Control of Permanent Magnet AC Machines for Traction Applications‘ was followed with a Post-Doc project ‘ELVAS: Electronic Valve Actuation Systems‘  funded under the EU Framework V programme and in collaboration with Peugeot Cars and Johnson Controls. In this programme we were looking to replace the conventional camshaft in combustion engines with individually actuated electronic valves

  • Clark R.E., Stewart P., Jewell G.W. and Howe D., “ Tailoring force-stroke characteristics in medium-stroke linear reluctance actuators” IEEE INTERMAG International Conference on Magnetics. Amsterdam, Holland. Paper GU08, April 28-May 02, 2002.
  • Clark R.E., Stewart P., Jewell G.W. and Howe D., “ Tailoring force-stroke characteristics in medium-stroke linear reluctance actuators” IEEE Transactions on Magnetics, Vol.38, No.5, pp.3267-3269 2002.
  • Stewart P., Gladwin D. and Fleming P.J., “Multiobjective analysis for the design and control of an electromagnetic valve actuator” Proceedings of the Institute of Mechanical Engineers, Part D: Journal of Automobile Engineering. Vol. 221(5), pp. 567-577, 2007.
  • Stewart P., Clark R.E., Jewell G.W. and Fleming P.J., “Controllability analysis of multi objective control systems” IEE / IEEE International Conference on Computer aided Control System Design, Glasgow, Scotland, pp.74-79, 18-20 September, 2002.


conventional cam-driven valves (l) and electronically actuated valves (r)


Final packaging configuration in Peugeot’s CR Diesel range

My first Research Council funded project was the EPSRC Grant: GR/S97507/01 Zero Constraint Free Piston Energy Converter,

Lotus Free Piston Engine. Background: Exhaust emissions analysers (L), 100kW 3-phase inverter (C), Control Techniques 3-Phase AC Drive (R)

Collaborating Company: Lotus Engineering and Prof Rui Chen at the University of Loughborough.

The aim of the project was to realise and demonstrate a completely novel energy conversion technology, which has the potential for high efficiency, low emissions, and low manufacturing cost. Its main applications are likely to be in series hybrid vehicles and portable power generation. The technology is based around a single-cylinder free-piston internal combustion engine (ICE), which is run on a 4-stroke cycle, with an integral linear electromagnetic machine and electromagnetically operated poppet valves. By freeing the piston from crank shaft motion, it removes most of the constraints of crankrod-slider ICEs, and facilitates many advanced combustion strategies – by enabling variable compression ratio operation, throttle-free operation, different piston strokes during compression and expansion, and other previously unattainable piston trajectories. It represents, therefore, a major step change in ICE operating flexibility and offers unparalleled design scope.

  1. Chen R. ,Winward E., Stewart P. and Taylor B., “Quasi-Constant Volume (QCV) Spark Ignition Combustion”, 2009 SAE World Congress, April 20-23, 2009, Cobo Center, Detroit, MI, USA.
  2. Stewart P., Gladwin D., Stewart J., Chen R. and Winward E.,  “Improved decision support for engine in the loop experimental design optimisation. Part I and Part II.”,  Proceedings of the Institute of Mechanical Engineers Part D – Automobile Engineering Vol.224, No.2, pp. 201-218, 2009.