Parameter Identification Test Setup

This task may be performed using a number of numerical optimization techniques. Here (/) ( o) simply computed and plotted over a range of appropriate values (ro 0) and the minimum is found graphically. 

The test setup used in the friction identification experiments is shown in Fig. 9.9. Similar to the test setup shown in Fig. 9.4, only one of the two sliders is included in the setup. The working parts of the test setup are taken from an actual seat adjuster. Two encoders are used to measure the angular displacement of the lead screw and the motor. A load cell is used to measure the force exerted by the pneumatic cylinder. The input voltage and current to the DC motor are also measured. With the help of a controller regulating the current input to the DC motor [119,120], the slider is set to move at near constant preset velocities in the applicable range. The angular velocity of the motor is calculated by numerical differentiation of its measured angular displacement. The motor torque is calculated from the measured input current and the known motor s torque constant. See Table 9.2 for a list of instruments and components of this test setup. 

The measurement data corresponding to the accelerating (start of motion) and decelerating (end of motion) portions of each test is discarded and the resulting near 

Steady-State measurements is averaged and recorded as one data point. See Fig. 9.11 for a sample of the near steady-state measurement results. 

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Figure 9.7 shows a schematic view of the parameter identification test setup designed to perform focused experiments on a single slider system. The mathematical model of this system is presented in this section. This model forms the basis of the parameter identification method to be described in Sects. 9.3 and 9.6 below. As shown in Fig. 9.7, two rotary encoders are used to measure the angular displacements of the lead screw, 0, and the motor, 0m- A load cell is used to measure the force exerted by the pneumatic cylinder, R. The input current to the DC motor are also measured. The input torque to the system, Tm, is then calculated from this quantity and the known torque constant of the DC motor. 

Figure 9.8 shows the 3-DOF model of the parameter identification test setup. Similar to the system in Fig. 9.7, the model consists of three parts, i.e., DC motor, gearbox, and lead screw mechanism. These parts are connected to each other via couplings with torsional compliance. 

In the remainder of this chapter, the focus is on a single slider mechanism. Based on the setup in Fig. 9.4, a new test setup is developed for the system parameter identification. The mathematical model of this setup is described next. 

In this section, the parameter identification approach described in Sect. 9.3 is applied to the measurements performed using the test setup described in the previous section. 

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