Pressure Control of a Pneumatic Artificial Muscle Including Pneumatic Circuit Model

Abstract

Various applications using pneumatic artificial muscles (PAMs) have been developed in recent years. When the pressure of the PAM is controlled, it is desirable to position a pressure sensor at the control port of a servo valve through a pipeline for improvement in usability, environment resistance, and elimination of mechanical complexity. However, the responsiveness of the pressure control worsens due to the volume and pressure losses through the pipeline. In this paper, we propose a pneumatic circuit model to compensate for such losses through the pipeline and a method to estimate the pressure at the PAM inlet. The proposed method improves the responsiveness of the pressure control by positioning a pressure sensor at the control port of the servo valve. We developed an experimental apparatus that simulates the mechanism of our power assist robot, and it was used for performance evaluation experiments of the conventional and proposed pressure control methods. When a sinusoidal pressure target value with a frequency of 1.5 Hz and load mass of 8 kg was fed as input, the errors between the measured and target values in the conventional and proposed control were approximately 45 and 20 kPa, respectively. The reduced error confirmed that the responsiveness of the pressure control was improved by the proposed method.

The Effects of Manufacturing Parameters on Static Characteristics of Water Hydraulic Artificial Muscles

“…The rubber tube samples' hardness was measured at an interval of 6 mm along the axial direction, and the results were shown in Table 8. Combining with the formula (5)- (8) and formula (11), the theoretical curves affected by the rubber tube thickness and the experimental results are shown in Figure 9. Figure 9 shows that the influence of initial rubber tube thickness will increase with the contraction ratio and the trend of the experimental results is consistent with the theoretical curve.…”

“…PAMs have advantages such as low cost, simple installation, and good flexibility. PAMs are widely used in medical rehabilitation [4], industrial automation [5], robotics [6]- [8], and other fields [9] [10]. However, PAMs have low working pressure range and output force, limited transmission accuracy, and repeatability.…”

Modeling Inverse Airflow Dynamics Towards Fast Movement Generation using Pneumatic Artificial Muscle with Long Air Tubes

“…In experimental setups for skeletal muscle robots using PAM, thin and soft bendable tubes are practical because tubes are installed in the narrow spaces such as the inside of the robot body [10]. These tubes cause pressure transmission delays that degrade the control performance [12]. However, how to compensate for the pressure transmission delay in PAM control has not been carefully studied.…”

Pressure control based on reinforcement learning strategy of the pneumatic relays for an electric-pneumatic braking system

“…Moreover, a model of the effective area of the servo valve is used in conjunction with a 1 pneumatic model to figure out the dead zone issue. 10 Most of the studies have been conducted based on solenoid valves with accurate mass flow capabilities, whose response speed is sufficient to support continuous pressure regulation. However, for economic reasons, the solenoid valves widely used in EPBS are low-speed switching types, such as the valves in antilock brake system (ABS) and some types of PRV, and cannot support precise regulation of mass flow rate.…”