Modeling and Reconstruction of State Variables for Low-Level Control of Soft Pneumatic Actuators

Abstract

To further advance closed-loop control for soft robotics, suitable sensor and modeling strategies have to be investigated. Although there are many flexible and soft sensors available, the integration into the actuator and the use in a control loop is still challenging. Therefore, a state-space model for closed-loop low-level control of a fiber-reinforced actuator using pressure and orientation measurement is investigated. To do so, the integration of an inertial measurement unit and geometric modeling of actuator is presented. The piecewise constant curvature approach is used to describe the actuator’s shape and deformation variables. For low-level control, the chamber’s lengths are reconstructed from bending angles with a geometrical model and the identified material characteristics. For parameter identification and model validation, data from a camera tracking system is analyzed. Then, a closed-loop control of pressure and chambers’ length of the actuator is investigated. It will be shown, that the reconstruction model is suitable for estimating the state variables of the actuator. In addition, the use of the inertial measurement unit will demonstrate a cost-effective and compact sensor for soft pneumatic actuators.

Soft Robots: Implementation, Modeling, and Methods of control

“…A sensor has been integrated into the fiber-reinforced actuator inertial measurement unit (IMU) and pressure sensing) to correlate it with PCC modeling and control loop closures on pressure and chamber lengths [95]. Sensing is also addressed, with locations for length sensors on a soft-linked robot joint and configuration estimation recommended, all while reducing errors [96].…”

Model-Based Nonlinear Feedback Controllers for Pressure Control of Soft Pneumatic Actuators Using On/Off Valves

“…In the work of Wang et al (2019a ), a pneumatic model was used to control the bending angle of a pneumatic network actuator using a robust backstepping controller with two-way, two-position on/off valves. Sliding mode controllers are proposed by Ibrahim et al (2019 ; 2021 ) to control the pressure of a soft actuator using proportional valves. In the work of Chen et al (2020 ), a pneumatic model is included to control the bending angle of a fiber-reinforced actuator using two three-way, two-position on/off valves with a backstepping-based adaptive robust controller and sliding mode controller.…”

Adaptive Pincer Grasping of Soft Pneumatic Grippers Based on Object Stiffness for Modellable and Controllable Grasping Quality

“…Tian et al [27] proposed an analytical model of fibrillar adhesive SPAs. Ibrahim et al [28] presented an analytical model and observer-based feedback control of SPAs. Despite the presence of them, the modeling and control in such works only concerns actuator-level variables, such as bending angle and blocking force.…”