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Chapter 2: Analysing a drive system

This chapter considers a number of broader issues, including the dynamic of both rotary and linear systems as applied to drive, motion profiles and aspects related to the integration of a drive system into a full appucation. With the increasing concerns regarding system safety in oper-ation the risks presented to and by a drive are considered, together with possible approaches to their mitigation. | Chapter 2 Analysing a drive system To achieve satisfactory operation of any motion-control system all the components within the system must be carefully selected. If an incorrect selection is made either in the type or the size of the motor and or drive for any axis the performance of the whole system will be compromised. It should be realised that over-sizing a system is as bad as under-sizing the system may not physically fit and will certainly cost more. In the broadest sense the selection of a motor-drive can be considered to require the systematic collection of data regarding the axis and its subsequent analysis. In Chapter 1 an overview of a number of applications were presented and their broad application requirements identified. This chapter considers a number of broader issues including the dynamic of both rotary and linear systems as applied to drive motion profiles and aspects related to the integration of a drive system into a full application. With the increasing concerns regarding system safety in operation the risks presented to and by a drive are considered together with possible approaches to their mitigation. 2.1 Rotary systems 2.1.1 Fundamental relationships In general a motor drives a load through some form of transmission system in a drive system and although the motor always rotates the load or loads may either rotate or undergo a translational motion. The complete package will probably also include a speed-changing system such as a gearbox or belt drive. It is convenient to represent such systems by an equivalent system see Figure 2.1 the fundamental relationship that describes such a system is Tm TL Itot Bum 2.1 at where Itot is the system s total moment of inertia that is the sum of the inertias of the transmission system and load referred to the motor shaft and the inertia 35 36 2.1. ROTARY SYSTEMS Figure 2.1. The equivalent rotational elements of a motor drive system. of the motor s rotor in kg m2 B is the damping constant in N rad-1 s ưm