Performance evaluation of wireless MEMS accelerometer for reciprocating compressor condition monitoring

Abstract

With recent development in wireless communication and Micro Electro Mechanical Systems (MEMS) technology, it becomes easier to monitor rotating machinery conditions by mounting compact wireless MEMS accelerometers directly on the rotor. This has the potential to provide more accurate dynamic characteristics of the rotating machine and hence achieving high monitoring performance. In this paper, a tiny MEMS accelerometer together with a battery powered microcontroller is mounted on the flywheel to acquire the on-rotor accelerations of a two-stage reciprocating compressor. The measured acceleration data is streamed to a host computer wirelessly via Bluetooth Low Energy (BLE) module. The true tangential acceleration is reconstructed by combining two orthogonal outputs of the sensor, which contain gravitational accelerations. To evaluate the performance of the wireless sensor, three different fault conditions including intercooler leakage, second stage discharge valve leakage and asymmetric stator winding of the motor driver are simulated individually on the compressor test rig. To confirm the wireless sensor performance, an incremental optical encoder was installed on the compressor flywheel to acquire the Instantaneous Angular Speed (IAS) signal for comparison with signals from the wireless sensor. The experimental results show that the running status of the compressor can be remotely monitored, allowing different leakages and motor faults to be diagnosed based on the tangential acceleration reconstructed from a wireless on-rotor MEMS accelerometer.

Planetary gearbox fault diagnosis using an on-rotor MEMS accelerometer

“…The speed estimation algorithm presented in that study was tested on a rotor operating at a range of speeds between 200 RPM and 2000 RPM and, by comparing the results obtained using the MEMS accelerometer with the speed measured by the encoder, they confirmed that their method was robust and could be applied to rotors irrespective of the state of vibration and during both acceleration and deceleration [11]. As the authors of [7,12] explain, one of the most critical issues in using on-rotor MEMS accelerometers is obtaining the pure tangential acceleration from accelerometer outputs which also contain gravitational acceleration, in order to characterise the rotor dynamics precisely and use them for condition monitoring. In [7], they mounted a three-axial MEMS data logger on the flywheel of a reciprocating compressor to record the onrotor accelerations.…”

“…ADXL345 is small, three-axis accelerometer with high resolution (13-bit) with measurement range up to ±16g. It measures the dynamic acceleration resulting from motion as well as the static acceleration of gravity [12]. Therefore, the signals measured using on-rotor MEMS accelerometers contain the required rotor dynamic information as well as the gravitational accelerations, which have to be removed to obtain the rotor dynamics precisely.…”