Researches regarding the use of non-conventional actuators

The purpose of this article is to present relevant concepts about the study of electro-pneumatic circuits using fluidic muscle actuators. The fluidic muscle is a type of pneumatic actuator having an extensive history of technical applications in the biomechanical field since the 1955. After Introduction, the authors study two pneumatic circuits. In fact, the first pneumatic circuit in this paper has only one actuator (fluidic muscle 1-1), but the second pneumatic circuit has two actuators (fluidic muscles 2-1 and 2-2. Further on, the authors present two electro-pneumatic schematics, a simple electro-pneumatic circuit and another electro-pneumatic circuit with PLC (Programmable Logic Controller). This type of actuator is used in robotics, material handling, motion control, industrial field and other applications. The pneumatic and electro-pneumatic circuits given in this paper are made using FluidSim software from Festo. In this case, the fluidic muscles are only non-conventional actuators. However, in pneumatic installations as well as in electro-pneumatic installations, the non-conventional actuators have the following advantages: strength, compactness, reliability, low price, ease of assembly or disassembly from their circuits, etc. Of course, in practice are many types of fluidic muscles, which are used in electro-pneumatic installations.

On trajectory tracking control of fluid-driven actuators

Fluid-driven actuators are not only well-established in automation, but also a promising drive technology for collaborative robots. Their inherent compliance due to the compressibility of suitable fluids such as air, as well as their direct drive properties are advantageous safety features for human-machine collaboration. In this work, we provide an overview of different fluid-driven manipulators, namely fluidic muscle actuated ones, continuum manipulators, and those with rotary joints. For the latter, we introduce the mathematical model including mechanics and pressure dynamics and describe its properties such as strong nonlinearities, which make trajectory tracking control challenging. A model-based nonlinear cascaded controller is presented. Experimental results on a 6 degrees of freedom (DOF) prototype demonstrate the resulting trajectory tracking performance.

Adaptive Iterative Learning Control of Fluidic Muscle Driven Parallel Manipulators for Force Control With Sliding Mode Technique

In this paper, an adaptive iterative learning control (AILC) method combined with sliding mode technique is proposed to improve the force control performance for repeating tasks of fluidic muscle (FM) driven parallel manipulators. Different from the traditional iterative learning control method, the proposed AILC is to learn the controller time-varying parameters rather than to learn the control signals. Since the AILC is sensitive to non-repetitive disturbances, the sliding mode technique is introduced to enhance the robustness. Since no model information involved in the controller design, the proposed method is a complete data-driven method. Hence, the difficulty of obtaining accurate model is avoided. Simulation studies are performed on a two degrees of freedom FM driven parallel manipulator. Simulation results demonstrate that the proposed method can achieve high force tracking performance and robustness.