Soft pneumatic actuators offer great advantages compared to rigid ones, particularly due to their compliant nature, which allows them to adapt to uncertainties in the environment. As such, they enable human-safe interactions and are often applied to various applications, such as for example, soft grippers or wearable devices for human motion assistance. The presented research describes the process of design, development and finally control of two cost-effective bellow pneumatic actuators. The properties of the developed devices are experimentally assessed by performing three different types of experiments. In a first instance, the testing of blocking force was performed, followed by experimental assessment of velocity-displacement characteristics, and finally, the dynamical properties for sinusoidally forced motion were examined. It was shown that the actuator can provide over 100 N force and assure a contraction ratio over 40% of its full length, with maximum velocity exceeding 60 mm/s. Experimental responses to a sinusoidally forced motion allowed establishing that no significant change due to the fatigue, creep and relaxation occur in material properties. Finally, the positioning performances of both developed devices were assessed by employing PID and LQR controllers which allowed their precise position control with fast responses and steady-state errors within the 0.2 mm margin. The performed research gives some insights into the future development of the pneumatically driven mechatronics systems used for position control.

GEROLER hydraulic motors are known for their good value for money and their balance between simplicity, robustness, compactness, versatility and noise. Compared to axial hydraulic motors, GEROLER motors still represent a research area with the possibility of a significant contribution in terms of nonlinear dynamic behavior analysis. The aim of this research was experimental analysis of GEROLER motor dynamics at uneven load torque. Based on the obtained laboratory measurements, a black-box model for predicting the operating parameters using the artificial neural networks was developed. Two different neural network architectures were used: the simpler static multilayer feed-forward network and the more complex dynamic NARX neural network. From the obtained results, it appears that the multilayer feed-forward neural network provides acceptable results, while the dynamic NARX neural network provides more favorable results due to its flexibility in dealing with nonlinear dynamic systems. The research conducted represents a new approach for modeling and predictive analysis of the GEROLER engine.

This study describes the design, simulation, and development process of a rehabilitation glove driven by soft pneumatic actuators. A new, innovative finger soft actuator design has been developed through detailed kinematic and workspace analysis of anatomical fingers and their actuators. The actuator design combines cylindrical and ribbed geometries with a reinforcing element—a thicker, less extensible structure—resulting in an asymmetric cylindrical bellow actuator driven by positive pressure. The performance of the newly designed actuator for the rehabilitation glove was validated through numerical simulation in open-source software. The simulation results indicate actuators’ compatibility with human finger trajectories. Additionally, a rehabilitation glove was 3D-printed from soft materials, and the actuator’s flexibility and airtightness were analyzed across different wall thicknesses. The 0.8 mm wall thickness and thermoplastic polyurethane (TPU) material were chosen for the final design. Experiments confirmed a strong linear relationship between bending angle and pressure variations, as well as joint elongation and pressure changes. Next, pseudo-rigid kinematic models were developed for the index and little finger soft actuators, based solely on pressure and link lengths. The workspace of the soft actuator, derived through forward kinematics, was visually compared to that of the anatomical finger and experimentally recorded data. Finally, an ergonomic assessment of the complete rehabilitation glove in interaction with the human hand was conducted.

This study presents the design, development, and experimental assessment of soft pneumatic actuators for achieving bending motion utilizing vacuum pressure, with their final application to soft robotic grippers. A novel soft actuator design is introduced, satisfying the following design requirements: safe operation without the risk of explosion, the ability to achieve large angular bending while overcoming significant forces, and the use of soft materials that are resistant to material fatigue. A vacuum-driven soft bending actuator (VSBA) was designed, incorporating a cylindrical ribbed bellow geometry and an integrated limiting element within its structure. Two variations of the VSBA were fabricated, each differing in the materials and manufacturing processes employed. The first version employs a cylindrical ribbed bellow made of thermoplastic rubber (TPR), while the other versions utilize heat-shrinkable polymer materials, resulting in an innovative manufacturing process capable of producing actuators in various sizes and shapes. This contributes to the analysis of how actuator geometry affects performance and enables its miniaturization. The performance of the novel VSBAs were experimentally assessed through measuring the bending angle, blocking force, and angular velocity–angle characteristics. The results confirmed a maximum bending angle of 140° corresponding to a bending ratio of 78%, a maximum blocking force of 110 N, and maximum angular velocity of 520°/s at a vacuum pressure of −0.8 bar. Finally, a soft robotic gripper was developed, consisting of three newly designed VSBAs. Experimental assessments demonstrated the gripper’s capability to grasp objects of various shapes, with a maximum holding force of 28 N.

Today, we are witnessing an increasing trend in the number of soft pneumatic actuator solutions in industrial environments, especially due to their human-safe interaction capabilities. An interesting solution in this frame is a vacuum pneumatic muscle actuator (PMA) with a bellow structure, which is characterized by a high contraction ratio and the ability to generate high forces considering its relatively small dimensions. Moreover, such a solution is generally very cost-effective since can be developed by using easily accessible, off-the-shelf components combined with additive manufacturing procedures. The presented research analyzes the precision positioning performances of a newly developed cost-effective bellow PMA in a closed-loop setting, by utilizing a Proportional-Integral-Derivative (PID) controller and a Linear Quadratic Regulator (LQR). In a first instance, the system identification was performed and a numerical model of the PMA was developed. It was experimentally shown that the actuator is characterized by nonlinear dynamical behavior. Based on the numerical model, a PID controller was developed as a benchmark. In the next phase, an LQR that involves a nonlinear pregain term was built. The point-to-point positioning experimental results showed that both controllers allow fast responses without overshoot within the whole working range. On the other hand, it was discovered that the LQR with the corresponding nonlinear pregain term allows an error of a few tens of micrometers to be achieved across the entire working range of the muscle. Additionally, two different experimental pneumatic solutions for indirect and direct vacuum control were analyzed with the aim of investigating the PMA response time and comparing their energy consumption. This research contributes to the future development of the pneumatically driven mechatronics systems used for precise position control.