Power supply and measurements system using dSpace

The dSpace system is a powerful engineering tool for monitoring, measuring and testing the mechatronics systems It has the following hardware and software parts:

• DS1005 PPC processor,

• PWM control board DS5101,

• conversion board measure DS2004,

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• Matlab/Simulink used to control the card and system (Real Time Workshop: RTW),

• compiler for the implement the initial command for the computer,

• tool to design the user interface control system.

The type DS1005 controller, the power converter, and type DS2004 high-speed A/D board have been used. The DS1005 controller has a processor board providing the possibility for real-time monitoring, and also functioning as an interface to the I/O boards and the host PC (Fig. 6.33).

The used power supply is based on the voltage fed, resonant, and full-bridge topology.

Fig. 6.33 System for power supply and measurements of the prototype MPM using dSpace

laboratory stand

Tab. 6.1 Power supply characteristics

Parameters Specifications Observations

Inductive loads

Voltage 0V  300 V

PWM frequency 0  200 kHz PWM

Minimum time out 25 ns

Accuracy 25 ns

Maximum current 4 A

Power 900W phase transition

40W continuous mode

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Capacitive loads Mode sinusoidal

Output Voltage 0V  1000 V maximum peak

Output current 0  1 A maximum sinusoidal peak

Power supply loads Resistance 1kΩ  100kΩ

Capacity 1nF  100nF

Output frequency 30kHz 50kHz Basic wave

Mode continuous Output voltage 1000 VDC

Output current 100mA DC 1A (maximum) Frequency cycles 100 Hz (maximum)

Load Resistance 10kΩ to 100 kΩ

Capacity 100nF to 1μF

The dSpace laboratory stand is shown in the Fig. 6.34. Matlab and dSPACE have been used to control the power supply for the prototype MPM. A simple program used to modify the resonance frequency, output amplitude and phase has been developed (Fig. 6.35). The main program blocs have been described in the appendix 5.

DSPACE

DC POWER SUPPLY

POWER CONVERTER DSPACE PC USER INTERFACE

MULTICELL PIEZOELECTRIC MOTOR CONVERSION BOARD

DS2004

Fig. 6.34 dSpace laboratory stand at the Laboratory LAPLACE (INP-ENSEEIHT, Toulouse) used to test the prototype MPM

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OUTPUT AMPLITUDE CONTROL

PHASE CONTROL

RESONANCE FREQUENCY CONTROL

START/STOP PANEL

Fig. 6.35 The Matlab – Control Desk interface used to control the power supply parameters

Using this program you can control the output voltage amplitude from 0 to 1000V (Tab. 6.1). For the final measurements, the output voltage amplitude has been set at approx.

400V, i.e., its value was almost twice as high as in the measurements using simplified linear power supply. The results of the torque vs. speed measurements have been presented in Fig.

6.36. The values of the blocking torque and the speed are following:

 blocking torque ≈ 0.4 Nm

 velocity ≈ 46 - 48 rpm.

Fig. 6.36 Torque vs. speed characteristic of the prototype MPM: calculated (using analytical model) - blue color, measured - green color

103 The measurements of the torque vs. speed characteristic (Fig. 6.36) of the prototype MPM have been carried for three points, It can be considered as sufficient, since for the prototype MPM the most important points for this characteristic are following: point referred to the blocking torque, and velocity at no-load as well. In turn, the measured coordinates of the third point “c” depend on various factors, e.g., the proper contact adjustment between rotor and stator, the kind of lubrication on the rotor or the rotor driving force. While testing the prototype MPM it has appeared that an interesting issue was the number of the used Smalley springs. The prototype MPM has symmetrical structure and during the measurements four springs on each side have been used. When the number of these springs has been reduced then the velocity has become higher, but torque become lower, and the time response become longer as well. This was due to not properly adjusted rotor - stator contact. On the other hand, the increased number of these springs has caused a higher driving torque, and better performance features of the prototype MPM but the velocity has been decreased. As was mentioned above, the purpose of this effort was to obtain the velocity of the prototype MPM as high as possible, and generating a appropriate torque value (the value has been achieved) as well.

Comparing for the prototype MPM the measured and calculated results, it can be concluded that the calculated results have a satisfactory compliance level with the measured ones. However, it should be pointed out that the obtained compliance level could be higher, if the difference between the calculated (26.2. kHz) and real resonance frequencies (22.0-22.2 kHz) were smaller. Moreover, a properly adjusted rotor - stator contact has also an essential influence on the compliance level.

To explain further the issue of the obtained compliance level for the prototype MPM, the torque vs. speed characteristic of the rotating-mode motor considered in [6] has been shown in Fig.

6.37. It can be noticed that for this motor the measured values of the blocking torque and the speed are following: blocking torque ≈ 0.14 Nm, and velocity ≈ 54 rpm.

The highest difference between calculated and measured results for those motor is at the point of maximum velocity. The measured and calculated values of the blocking torque are practically the same.

Fig. 6.37 Torque vs. speed characteristic of the rotating-mode motor described in [6]

104 It should be noticed that the prototype MPM has lower maximum velocity comparing to the referred rotating-mode motor (47 rpm vs. 54 rpm, respectively), however it has almost three times higher blocking torque (0.4 Nm vs 0.14 Nm, respectively). The results show an advantage of the prototype MPM over the referred rotating-mode motor [6].

6.6 C

The prototype MPM counter-masses and housing have been made using 3D printer. The input materials to the printer were following: aluminum and nylatron respectively. In turn, the other parts of the prototype MPM have been made on milling machine using steel.

The measured parameters of the prototype MPM are following:

 resonance frequency – 22 kHz,

 displacements at the contact rotor/stator point – 1.1 m,

 speed– 46 - 48 rpm,

 blocking torque – 0.4 Nm.

Comparing for the prototype MPM the measured (shown above) and calculated results (speed 40 rpm and blocking torque 0.6 Nm), you can conclude that the calculated results have a satisfactory compliance level with the measured ones.

It should be noticed that for the prototype MPM the most important points for the torque vs.

speed characteristic are following: point referred to the blocking torque, and velocity at no-load as well.

The prototype MPM testing has shown that an interesting issue is the applied number of the Smalley springs. Reducing the numbers of the springs decreases torque and increases velocity.

On the other hand, increasing the number of those springs generates higher driving torque, but the speed is decreasing, and the MPM has better performance features.

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