Material from this thesis has been published as follows: 1. Wang, J., Yang, L., Luo, X. and Mangan, S. (2010). ‘Mathematical modelling study of scroll air motors and energy efficiency analysis - Part I’, accepted by IEEE/ASME Transactions on Mechatronics, Digital Object Identifier: http://dx.doi.org/10.1109/TMECH.2009.2036608, U.S.A. 2. Wang, J., Luo, X. Yang, L. Shpanin, L., Jia, N., Mangan, S. and Derby, J.W. (2010). ‘Mathematical modelling study of scroll air motors and energy efficiency analysis - Part II’, accepted by IEEE/ASME Transactions on Mechatronics, Digital Object Identifier: http://dx.doi.org/10.1109/TMECH.2009.2036607, U.S.A. 3. Luo, X., Wang, J. and Sun, H. (2010). Control and energy efficiency analysis for a pneumatic-electrical system, The Proceedings of the UKACC International Conference on Control 2010, 7-10 September, Coventry, U.K. 4. Luo, X., Sun, H. and Wang, J. (2009). Air leakage study for energy efficiency improvement of a pneumatic-electricity conversion system, The Proceedings of the 15th International Conference on Automation and Computing, 19 September, Luton, U.K. 5. Luo, X., Jia, N., Shpanin, L.M. and Wang, J. (2008). An energy efficient pneumatic-electricity system – modelling study of the scroll expander, The Proceedings of the 11th Mechatronics Forum Biennial International Conference, 23-25 June, Limerick, Ireland. 6. Luo, X., Wang, J., Shpanin, L.M., Jia, N., Liu, G. and Zinober, A. (2008). Development of a mathematical model for vane-type air motors with arbitrary N vanes, The Proceedings of World Congress on Engineering 2008, 2-4 July, London, U.K.