TEST SYSTEM WITH CONFIGURABLE CLOSED LOOP

• US 20130150984A1
• Filed: 12/13/2011
• Published: 06/13/2013
• Est. Priority Date: 12/13/2011
• Status: Abandoned Application

• Current Assignee: Avtron Aerospace, Inc. (Testek Solutions)
• Original Assignee: Avtron Aerospace, Inc. (Testek Solutions)
• Inventors: Nigro, Richard M., Wehrung, Gregory E., Glynn, Daniel P., Oleksy, Christopher F.
• Application Number:
  US13/324,270
• Publication Number:
  US 20130150984A1
• Time in Patent Office: Days
• US Class Current: 700/37
• CPC Class Codes: G05B 11/42 for obtaining a characteristic which is both proportional and time-dependent, e.g. P. I., P. I. D.

Abstract

A test system can comprise a controller configured to provide a closed loop. The closed loop can comprise a forward transfer function with programmable coefficients that is configured to receive a signal corresponding to a command signal. The closed loop can also comprise a feedback transfer function having programmable coefficients and can be configured to provide a feedback signal that is subtracted from the command signal. The controller can be configured to provide a control signal corresponding to an output of the forward transfer function.

Claims

1. A test system comprising:

a test controller configured to provide a closed loop, the closed loop comprising;

a forward transfer function with programmable coefficients that is configured to receive a command signal; and

a feedback transfer function having programmable coefficients and being configured to provide a feedback signal that is subtracted from the command signal;

wherein the test controller is configured to provide a control signal corresponding to an output of the forward transfer function.

2. The system of claim 1, wherein the test controller further comprises an FPGA.

3. The system of claim 1, the closed loop further comprises a proportional-integral-derivative (PID) controller with programmable proportional, integral and derivative parameters, an output of the PID controller being provided as an input to the forward transfer function.

4. The system of claim 1, wherein the closed loop further comprises a dither function that is configured to apply a dithering to an output of the forward transfer function, the dithering including a programmable frequency and magnitude.

5. The system of claim 1, wherein the feedback transfer function is a first feedback transfer function and the feedback signal is a first feedback signal, the closed loop further comprising a second feedback transfer function having programmable coefficients and being configured to provide a second feedback signal to the PID controller.

6. The system of claim 1, wherein the closed loop further comprises a programmable feedback gain block configured to apply gain to the feedback signal in response to a user input.

7. The system of claim 1, wherein the command signal comprises a plurality of command signals, and the system further comprising a command module configured to provide the plurality of command signals that control an output of the forward transfer function.

8. The system of claim 1, further comprising a current driver configured to receive the control signal from the FPGA, the current driver being configured to provide a control current to an output that corresponds to the output of the FPGA, the output configured to connect with a unit under test (UUT).

9. The system of claim 8, wherein the UUT comprises an electro-hydraulic valve (EHV) that is operated based on the control current.

10. The system of claim 9, wherein the UUT further comprises a linear variable differential transformer (LVDT) that is configured to provide a signal corresponding to the feedback signal based on a sensed parameter of the UUT.

11. The system of claim 10, wherein the signal provided by the LVDT corresponds to a position of the UUT actuator.

12. The system of claim 1, wherein the forward transfer function is configured such That

f[p_n]=a₁*f_n−

1+a₂*f<sub>n−

2</sub>+a₃*f<sub>n−

3</sub>+a₄*f<sub>n−

4</sub>+b₀*p_n+b₁*p<sub>n−

1</sub>+b₂*p<sub>n−

2</sub>+b₃*p<sub>n−

3</sub>+b₄*p<sub>n−

4</sub>;

wherein;

p_n denotes an input of the forward transfer function;

f[p_n] denotes an output of the forward transfer function for a given p_n; and

a₁, a₂, a₃, a₄, b₀, b₁, b₂, b₃ and b₄ denote the programmable coefficients of the forward transfer function.

13. The system of claim 12, wherein the reverse transfer function is configured such that:

y[x[n]]=a₁*y<sub>n−

1</sub>+a₂*y<sub>n−

2</sub>+a₃*y<sub>n−

3</sub>+a₄*y<sub>n−

4</sub>+b₀*x_n+b₁*x<sub>n−

1</sub>+b₂*x<sub>n−

2</sub>+b₃*x<sub>n−

3</sub>+b₄*x<sub>n−

4</sub>

wherein;

x[n] denotes an input to the feedback transfer function;

y[x[n]] denotes a signal output by the feedback transfer function for a given input signal; and

a₁, a₂, a₃, a₄, b₀, b₁, b₂, b₃, b₄ are coefficients for the feedback transfer function.

14. The system of claim 1, wherein a source of the feedback signal is selectable.

15. The system of claim 1, wherein the closed loop comprises a plurality of closed loops, each of the plurality of closed loops having a programmable transfer function.

16. A test system for configuring a closed loop comprising:

a control system configured to provide a closed loop, the closed loop configured to receive at least one command signal and comprising;

a proportional-integral-derivative (PID) controller with programmable constants;

a forward transfer function with programmable coefficients that is configured to receive an output of the PID controller; and

a feedback transfer function having programmable coefficients and being configured to provide a feedback signal to the PID controller;

wherein the control system is configured to provide a control signal corresponding to an output of the forward transfer function;

an interface configured to provide an electrical signal to an output for operating a unit under test (UUT) as a function of the electrical signal.

17. The system of claim 16, wherein the interface further comprises a demodulator configured to demodulate the response signal and provide the feedback signal to the control system.

18. The system of claim 16, wherein the forward transfer function comprises a difference equation corresponding to a plurality of variables with coefficients.

19. The system of claim 16, wherein the closed loop comprises a plurality of closed loops.

20. A method for configuring a test system comprising:

selecting a feedback signal for a closed loop from a plurality of feedback signals;

setting transfer function parameters in a transfer function of a control system for the closed loop; and

setting proportional-integral-derivative (PID) controller parameters for a PID controller of the control system for the closed loop.

21. The method of claim 20, wherein the setting of the transfer function parameters further comprises:

setting coefficients for a difference equation corresponding to a forward transfer function; and

setting coefficients for a difference equation corresponding to a feedback transfer function of the control system for the closed loop, wherein an output of the feedback transfer function corresponds to an input of the PID controller.

22. The method of claim 21, further comprising setting dither parameters for a dither function of the control system for the closed loop, wherein an input to the dither function corresponds to an output of the forward transfer function.