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This chapter explains the role of speed-controlled drives in general automation and industrial robots, identifies the basic elements of the speedcontrolled system, defines the control objective, and devises control strategies. Fundamental terms related to continuous-and discrete-time implementation are defined. An insight is given into the role and characteristics of the torque actuator, comprising the servo motor and the power converter. Separately excited DC motor coupled with an inertial load is analyzed as a sample speed controlled system.

In this chapter, the basic speed-controller design concepts are analyzed. Considering proportional and integral control actions, the key transfer functions are derived, and design goals formulated. An insight is given into the closed-loop bandwidth and the parameter setting. Discussing the impact of various disturbances on the speed controller structure, the feedforward control and internal model principle are explained. Laplace transform basics and familiarity with computer simulation tools are required to understand the developments and examples in chapters 2 and 3.

Practical speed controlled systems comprise delays in the feedback path. Their torque actuators, with intrinsic dynamics, provide the driving torque lagging with respect to the desired torque. Such delays have to be taken into account when designing the structure of the speed controller and setting the control parameters. In this chapter, an insight is given into traditional DCdrives with analog speed controllers, along with practical gain-tuning procedures used in industry, such as the double ratios and symmetrical optimum.

Contemporary motion control systems comprise discrete-time speed and position controllers. This chapter restates the basic concepts of discretetime control, and provides the means to analyze, design, implement, and evaluate discrete-time speed controllers. The sampling process is reviewed and explained. The system dynamics are described in terms of difference equations. The -transform is introduced as the means of converting the difference equation into an algebraic form, thus simplifying the analysis, design, and performance prediction of discrete-time controllers. The ztransform definition and properties are restated. Before discussing and designing the structure of discrete-time speed controllers, the signal flow between the discrete-time controller and continuous-time control object is explained and detailed. The optimization rule is devised and the parameter setting procedure proposed. In closing sections of the chapter, the large step response is analyzed, explaining the system limits and the wind-up phenomenon. The speed controller structure is enhanced in order to preserve the response character and avoid overshoots and oscillations with large input and load disturbances.

In this chapter, position control and its role within motion-control systems is introduced and discussed. Single-axis position controllers are explained and modeled. Analytical design of the position controller structure is given, along with procedures for setting the adjustable feedback parameters. The speed and torque system limits are explained at the end of the chapter, along with the analysis of nonlinear operating modes. Nonlinear control laws, capable of securing a robust large step response, are considered.

A position controller with integral action suppresses the output error caused by a constant load. It also provides the system with the capability of tracking the constant slope profile without an error. In this chapter, the controller structure and parameter setting are considered for linear operating mode. The ability of the system to track the reference trajectory is discussed. The impact of the controller structure and the trajectory properties is evaluated. For the operation with large input disturbances, where the torque and speed limits of the system are reached, a nonlinear modification of the discrete-time position controller is proposed, providing a robust, aperiodic, and time-optimal response to large disturbances.

In the majority of applications, position-controlled systems track predefined position reference profiles or trajectories. In this chapter, the tracking error is defined and expressed in terms of the reference profile derivatives and the position controller gains. Computer simulations are used in order to explore the error reduction achieved by the proper shaping of the profile. The reference profile generation is described and explained. The trajectory generation problem is defined as devising the function that changes between the given points. The time derivatives of the function are to be restricted, and with higher-order derivatives preferably equal to zero. The analytical considerations and simulation runs are included, relating the tracking error and the peak torque requirement to the profile time derivatives. In the closing section, interpolation of reference profiles is introduced, explained, and demonstrated.

This chapter explains the mechanical resonance and torsional oscillations within mechanical structures of the motion-control systems. Their impact on closed-loop performance is predicted and evaluated. The cases are distinguished where the lowest resonance frequency remains well beyond the desired bandwidth and where the resonant modes can be neglected as secondary phenomena. For applications where the resonance phenomena overlap with the frequency range of interest, passive and active antiresonant control actions are devised and evaluated. An insight is given into designing and using antiresonant controllers by means of simulation and experiments.