In this article, a novel error-driven variable gain active disturbance rejection control (ADRC) approach is developed for pneumatic servo system, and the desired performance of trajectory tracking and the disturbance rejection can be guaranteed. The proposed variable gain ADRC includes three parts: 1) variable gain tracking differentiator (TD); 2) variable gain extended state observer (ESO); and 3) variable gain error feedback controller (EFC). The proposed variable gain TD is noise tolerant and possesses a variable gain, which can be dynamically adjusted according to the tracking error, and the performance for tracking the reference signal and extracting its derivative is improved. The variable gain ESO is also equipped with a variable gain driven by estimation errors to improve the estimation performance. Then, the variable gain EFC is further designed to improve control accuracy. Finally, simulations and experimental results are presented to verify the efficiency of the proposed methods.

Ultrasonic gas leak location technology is based on the detection of ultrasonic waves generated by the ejection of pressured gas from leak holes in sealed containers or pipes. To obtain more accurate leak location information and determine the locations of leak holes in three-dimensional space, this paper proposes an ultrasonic leak location approach based on multi-algorithm data fusion. With the help of a planar ultrasonic sensor array, the eigenvectors of two individual algorithms, i.e., the arrival distance difference, as determined from the time difference of arrival (TDOA) location algorithm, and the ratio of arrival distances from the energy decay (ED) location algorithm, are extracted and fused to calculate the three-dimensional coordinates of leak holes. The fusion is based on an extended Kalman filter, in which the results of the individual algorithms are seen as observation values. The final system state matrix is composed of distances between the measured leak hole and the sensors. Our experiments show that, under the condition in which the pressure in the measured container is 100 kPa, and the leak hole–sensor distance is 800 mm, the maximum error of the calculated results based on the data fusion location algorithm is less than 20 mm, and the combined accuracy is better than those of the individual location algorithms.

In this article, a multi-DOF manipulator driven by novel hysteresis-attenuated pneumatic artificial muscles (PAMs) is designed, and the multi-DOF manipulator is composed of three manipulator units assembled in cascade, and each manipulator is driven by hysteresis-attenuated PAMs. Compared with the conventional McKibben PAMs, the proposed hysteresis-attenuated PAMs is improved structurally to attenuate the undesired hysteresis by implanting a compression spring. Moreover, the mathematical models of both the hysteresis-attenuated PAMs and the multi-DOF manipulator are established. Finally, comparison test results show that the hysteresis is attenuated effectively for the hysteresis-attenuated PAMs, and the experimental results show that good control performances are achieved for the multi-DOF manipulator under different loads and pressures.

Vibrating wire sensors are widely used in long-term static strain monitoring. However, when dynamic measurements are needed, conventional measuring methods are unsuitable. On the basis of the static measuring method, in this paper we propose a new method of dynamic frequency excitation and measurement based on vibrating wire sensors. In the dynamic frequency excitation method, we adopt intermittent self-adaptive excitation which allows the internal steel in the sensor to vibrate continuously, without attenuation. In turn, this allows us to continuously collect and analyze the sensor signal. We use a dynamic frequency measurement algorithm to subsequently process the data, which interpolates three spectral lines based on a windowed fast Fourier transform. The resonance frequency of the sensor is obtained, which then allows us to dynamically acquire the strain. Through data analysis, the theoretical calculation error of the resonance frequency can be obtained to within 0.015 Hz, and the theoretical sampling rate of dynamic strain measurement can reach to 325 Hz. In addition, through our experiments, the efficiency and the feasibility of our methods are verified.