Servomotors

Higher education teachers: Jarm Tomaž
Collaborators: Kramar Peter

Subject description

Prerequisits:

• Inscription to 2nd year study.
• Positive grade for lab work is a prerequisite to enter the final exam.
• The majority of practical lab assignments must be successfully finished and defended (a report) to get a positive grade.

Content (Syllabus outline):

Mathematical tools for description of servomotors and electromechanical systems. Electric motor fundamentals. Electromechanical analogies, electrical and mechanical properties of some commonly used servomotor type. DC motors controlled by armature current and stator magnetic field: basic properties, implementations, calculation of losses, transfer functions. Heat losses, heat transfer function, temperature dependence of motor parameters. The impact of type of power supply on servomotor response. The resonance in a electromechanical system. Brushless DC motors. Asynchronous AC servomotors: physical principles of operation and main properties. Stepper motors: permanent magnet, variable reluctance and hybrid stepper motors; static moment and positioning error, torque-speed characteristic. Power supply and control of DC, asynchronous AC and stepper motors. Physics of hydraulic flow of fluid under pressure. Hydraulic servomotors of different types. Electrohydraulic controllers, different combinations and static characteristics of controllers and hydraulic-motors. Transfer function of hydraulic and electrohydraulic systems. Nonlinear properties of hydraulic elements, Coulomb friction, linearization of characteristics.

Objectives and competences:

To learn about physical principles and working properties of various servomotor types (electric and hydraulic). To get insight into mathematical modeling and estimation of servomotor transfer function estimation and into application of different servomotor types with respect to their characteristics.

Intended learning outcomes:

• Knowledge and understanding: To understand physical principles of operation and main properties and applications of different types of servomotors. To understand the role of various parameters on the dynamics of servomotors.
• Application: Use of transfer functions to describe the input-output relationship between the controlling and controlled variables in servomotors. Measurement and determination of parameters of different servomotors. Application of a servomotor in a controlled system with electric or electrohydraulic actuators.
• Reflection: To be able to estimate and chose a suitable motor for application in a servosystem.
• Transferable skills: To gain knowledge and develop skills for mathematical modelling of electromechanical and electrohydraulic systems and for evaluation and comparison of different solutions.

Learning and teaching methods:

The next teaching methods will be used: lectures and practical lab work.

• Lectures: Formal transfer of fundamental knowledge and data using theoretical and mathematical explanations and supported with graphical tools (images, movies) and computer simulations. Exercises in solving problems concerning servomotor analysis and performance.
• Lab vork: practical assignments to support the material covered in lectures, on which the students work in pairs. Some of the lab work may be conducted in a form of larger mini-projects on topics not neccessarily covered in lectures. Practical work consists of measurement and determination of of static and dynamic properties of motors and of performance testing of electromechanical systems. The students are requested to self-study and to prepare for the assignment. Reports must be written for all practical assignments.

Study materials

Readings:

1. A. Hughes, Electric motors and drives, 4th ed., Newnes/Elsevier, 2013.
2. R. Firoozian, Servo Motors and Industrial Control Theory. Springer, 2008
3. N.D. Manring, Hydraulic control systems, Wiley, 2005.