Background:
Vibration control loop is the key technology adopt to improve the control performance of vibration table, which is set outside of the hydraulic vibration table servo control loop. However, the huge number of signal processing work prompts high demands on the calculation ability of the vibration controller. One kind of multi-CPU embedded vibration controller constructed by Digital Signal Processor (DSP) is proposed considering the working principle of the hydraulic vibration table and the Power Spectrum Density (PSD) reproduction process. The embedded controller consists of an acquisition unit, a calculation unit, and a monitoring unit distributes vibration control tasks to different processing unit to realize distributed algorithm calculations. Every processing unit uses dual-port memory to accomplish data interaction between each other. The development of the embedded controller provides a benchmark engineering case for the design of the hydraulic vibration table vibration controller.
Objective:
This article focuses on the development of the multi-CPU embedded vibration controller and the distributed calculations. Meanwhile, the power spectrum density experiment is carried out to verify the performance of hydraulic vibration embedded controller.
Methods:
1) The structure of the hydraulic vibration table control system is given, that is, two closed-loop controls. The bandwidth of the system is further broadened by the vibration control of the outer loop. Besides, the accuracy of vibration control is also improved. Then, the development needs of the vibration controller is put forward according to the detail process of the power spectrum density replication.
2) An arithmetic processing unit is formed by using TI C2000 series DSP to calculate a large number of signal processing and a signal acquisition unit at a high speed. In order to improve signal processing efficiency, the signal acquisition unit is used to perform preprocessing calculations (data acquisition and filtering) and vibration control calculations in a distributed manner.
3) Processing speed is further improved by taking a full advantage of DSP software sources include lots of library functions and optimized assembly library functions.
4) The friendly operation of the controller and the safety monitoring of the experiment process are realized by the industrial computer served as the human-computer interaction unit.
5) Multi-CPU data sharing is achieved through using dual-port RAM to realize.
Results:
Through experiments, the developed embedded controller is fully estimated. The experiment shows that the developed hydraulic vibration table can realize real-time vibration control. Concerning the acceleration power spectrum density reproduction experiment, 256 acceleration response samples are calculated, and the update time is 4ms. The tracking accuracy of the time-domain waveform is controlled within 0.3%.
Conclusion:
The use of the developed embedded controller with a signal conditioning equipment can achieve real-time control of the hydraulic vibration table, but the performance of the embedded controller can be promoted in advance, and the performance improvement of the hydraulic vibration table embedded controller can be studied from the following aspects:
1)The Fourier calculation is executed by the acquisition unit to share the calculation workload of the calculation unit;
2) The computing unit uses a signal processor chip with better performance, although this will bring development difficulties;
3) The monitoring computer can use an embedded controller with superior performance instead of an industrial computer to reduce the size, improve the performance;
4) The DSP real-time operating system should be used and the task scheduling of vibration control experiments should be optimized.
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