Position Control and Force Allocation Algorithms for Hybrid Pneumatic-Electric Linear Actuators

Abstract

It has been shown that hybrid pneumatic electric actuators (HPEAs) can provide both accurate position control and high inherent safety, due to their low mechanical impedance; making them a suitable choice to be used in applications such as collaborative robots. HPEAs are redundant actuators that combine the large force, low bandwidth characteristics of pneumatic actuators with the large bandwidth, small force characteristics of electric actuators. If these characteristics are mathematically modelled, input allocation techniques can improve the HPEA performance by intelligently distributing the required input (force or torque) between the redundant actuators. In this study, after developing a model for a HPEA-driven system, a model-predictive control (MPC) approach is designed that employ this model and solve the position tracking and input allocation problem using convex optimization. Another approach based on conventional linear controllers is included and compared. Although the linear controller was more computationally-efficient, it was inferior to the MPC-based controller in position tracking and force allocation performance. The MPC-based controller with a two-layer structure reduced the position RMSE by 59%, the mean absolute electric actuator force by 36%, and the mean absolute pneumatic actuator force by 24% relative to the linear controller. It can also be computed fast enough for real-time operation.

Fusion Hybrid Linear Actuator: Concept and Disturbance Resistance Evaluation

“…However, the placement of two or more actuators at different positions may cause large joints and links when implementing conventional actuators with transmission elements such as cables, gears, and belts [7], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [27], [28], [29], [31]. In addition, when robots dedicated to interacting with humans are designed using the hybrid actuation approach, transmission mechanisms have to be covered for assured safety.…”

“…2(b) and (c), respectively. Rouzbeh et al [31] presented the parallel connection design, where the difference between the force of a macro actuator, having high force but low frequency, and that of a mini actuator, having low force but high frequency, caused a rotational moment at the contact point. Therefore, a linear guide to support the output shaft was essential in the parallel connection design.…”

Research on the smooth velocity control of a driving switching process of a new pneumatic electric hybrid actuator

“…Pneumatic actuators and electric actuators are more and more widely used in the field of industrial automation (Saravanakumar et al, 2017;Zhang et al, 2014), but they have their limitations. The pneumatic actuator has a large output force and fast movement velocity, but the positioning accuracy is low (Tan et al, 2019;Qi et al, 2020).…”

“…The electric actuator has a high positioning accuracy and good antiinterference performance, but the output force is small, and the cost is high under the long stroke (Wang et al, 2020;Qi et al, 2018). To meet the requirements of fast-moving and accurate positioning at the same time, hybrid actuators combined with pneumatic and electric drive have been focused on, which were called pneumatic-electric hybrid actuators (PEHAs; Paul et al, 2010;Zong et al, 2019;Rouzbeh et al, 2020).…”