Position/force control of master–slave antagonistic joint actuated by water hydraulic artificial muscles

Proceedings of the Institution of Mechanical Engineers, Part C:

Liu

et al. 2021

Self Cite

Compared with pneumatic artificial muscles (PAMs), water hydraulic artificial muscles (WHAMs) have the advantages of high force/weight ratio, high stiffness, rapid response speed, large operating pressure range, low working noise, etc. Although the physical models of PAMs have been widely studied, the model of WHAMs still need to be researched for the different structure parameters and work conditions between PAMs and WHAMs. Therefore, the geometry and the material properties need to be considered in models, including the wall thickness of rubber tube, the geometry of ends, the elastic force of rubber tube, the elongation of fibers, and the friction among fiber strands. WHAMs with different wall thickness and fiber materials were manufactured, and static characteristic experiments were performed when the actuator is static and fixed on both ends, which reflects the relationship between contraction force and pressure under the different contraction ratio. The deviations between theoretical values and experimental results were analyzed to investigate the effect of each physical factor on the modified physical model accuracy at different operating pressures. The results show the relative error of the modified physical model was 7.1% and the relative error of the ideal model was 17.4%. When contraction ratio is below 10% and operating pressure is 4 MPa, the wall thickness of rubber tube was the strongest factor on the accuracy of modified model. When the WHAM contraction ratio from 3% to 20%, the relative error between the modified physical model and the experimental data was within ±10%. Considering the various physical factors, the accuracy of the modified physical model of WHAM is improved, which lays a foundation of non-linear control of the high-strength, tightly fiber-braided and thick-walled WHAMs.

Section: Wall Thickness Model Of the Rubber Tubementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A modified physical model of high-strength water hydraulic artificial muscles considering the effects of geometry and material properties

Proceedings of the Institution of Mechanical Engineers, Part C:

Liu

et al. 2021

Self Cite

“…The artificial muscle has made significant progress in structures and materials, 17,18 actuation, 19,20 modeling analysis, 21 and sensor control. 22,23 However, the long-term service capability is also crucial. 24 Currently, the fatigue research of artificial muscles mainly focuses on pneumatic artificial muscles (PAMs).…”

Section: Introductionmentioning

confidence: 99%

Analysis on fatigue behavior of water hydraulic artificial muscles under different elastic loads in underwater environment

Fatigue Fract Eng Mat Struct

et al. 2023

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As a novel and flexible actuator, the water hydraulic artificial muscle (WHAM) has become at the forefront of bionic robot research. In order to explore the fatigue behavior of WHAM, the lifetime of WHAM was analyzed based on the crack propagation of neoprene rubber and the S‐N curve of aramid fiber. Meanwhile, WHAM's fatigue tests were carried out, and the fatigue life exceeded 56,000 cycles under the pressure of 2 MPa and the elastic load of 1030.7 N/mm. In addition, WHAM's fatigue failure is represented as the burst of the rubber tube after fiber fracture. Moreover, heavy load aggravates fibrillation that leads to severe fracture of fibrils under similar friction, and the fatigue life of WHAM is aggravatingly shortened by the coupling of fibrillation and friction. Finally, an empirical model of fatigue life was obtained, which can predict the lifetime of WHAM.

“…For example, to carry more than 20 kN of tension, the diameter of the wire rope must be at least 6 mm. The water hydraulic artificial muscle developed by Zhang et al 4 and Ning et al 5 can output a force of more than 20 kN, but uses a rope with a diameter of 8 mm on the joint. Experimental results have revealed that the actual joint rotation angle will be smaller than the theoretical value owing to the excessive rigidity of wire rope.…”

mentioning

confidence: 99%

Modeling of fibrous tow transmission considering residual strain and friction

Textile Research Journal

Hou

et al. 2021

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This study established a mechanical model based on the mechanical properties of fibrous tows and their force of interaction with spools. The proposed model not only describes the hysteresis, nonlinear elastic, and viscoelastic stress components, but also analyzes the effect of residual strain on aramid fiber mechanical properties. Moreover, the effect of the interaction force between the fiber and spool on the transmission accuracy should be considered. Contrary to the conventional view, hysteresis is caused not only by internal sliding among molecules and molecular chains but also by friction between the fibers and spools. To assess this effect, several monotonous and cyclic tensile tests were conducted, with the results showing that the maximum relative error of the mechanical model did not exceed 5%. The proposed mechanical model can help designers determine effective carrying ranges and predict the fiber mechanical behavior, thereby laying a foundation for achieving nonlinear control of the fibrous tow transferring load.