Benchmarking Force Control Algorithms

Vicario, Rudy; Calanca, Andrea; Dimo, Eldison; Murr, Noè; Meneghetti, Matteo; Ferro, Rafael Medina; Sartori, Enrico; Boaventura, Thiago

doi:10.1145/3453892.3461332

Cited by 5 publications

(6 citation statements)

References 5 publications

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“…The control strategy is a crucial element during the design process of SWRR. The control strategy's objective is to track the device's trajectory [ 56 ] and/or forces [ 57 ] to plan the desired action to apply a stimulus to the actuator later to generate a movement. This process is similar to the motor control of the human body, where the central nervous system plans the movement base on sensory information and sends the command to drive the muscles.…”

Section: Discussionmentioning

confidence: 99%

Soft Wearable Rehabilitation Robots with Artificial Muscles based on Smart Materials: A Review

Gonzalez-Vazquez

Garcia

Kilby

et al. 2023

Advanced Intelligent Systems

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During the past decade, wearable devices such as exoskeletons have gained popularity [1] in different fields, such as the military, [2] industry, [3] and rehabilitation. [4] In the latter, rehabilitation exoskeletons are used to restore or maintain the functionality and mobility of people with physical disabilities. [5] These are receiving greater attention as the number of people with disabilities affecting physical performance will increase in the following decades as the population ages and individuals live longer with noncommunicable conditions (e.g., cerebral palsy, stroke, acquired brain injuries, and muscular dystrophies). [6][7][8] Most current exoskeletons use electric motors and rigid links to realize actuation and often have heavy and bulky designs that are difficult to safely wear outside clinical facilities. [9] Hence, researchers in this area are working to develop soft wearable rehabilitation robots (SWRRs), featuring soft actuators that are agreeable to the users as they have increased compliance, adaptability, comfort, safety, and less weight. [10][11][12] Currently, SWRR relies mainly upon two soft robotic technologies, cable-driven and fluidic actuators. For a cable-driven system, the wire is embedded into clothes or tubes and attached to an anchor point. The other side of the wire is connected to an electric motor to generate the desired movement and force by pulling the cable [13,14] (Figure 1a). Alternatively, in fluidic actuation (Hydraulic/Pneumatic), a pressurized fluid is inserted into a chamber made of highly deformable material to generate a displacement [11,15,16] (Figure 1b). However, these require large and heavy external pumps and valves to compress the fluid. [17] Unfortunately, cable-driven and fluidic actuation need cumbersome components (e.g., electric motors, pumps, and valves) to work, compromising the portability of the systems when used in daily life. [18] Therefore, in recent years, research has been committed to developing new actuator technologies that can overcome the drawbacks of the current actuators used in SWRR. These technologies include artificial muscles based on smart materials (AMSMs). AMSMs are soft actuators composed primarily of material with a low Young's modulus similar to that of soft biological materials (10 ^4-10 ^9 Pa) that can sense and directly convert physical stimulus (e.g., light, electrical, heat) into physical displacement. [19][20][21][22][23] Some examples of smart materials are shape-memory alloy (SMA), [24] dielectric elastomer actuators (DEAs), [25] ionic polymer-metal composites (IPMC), [26] shapememory polymers (SMPs), [27] and twisted and coiled polymer actuators (TCPs). [28] Due to their inherent properties and manufacturing processes, AMSM can be fabricated in various shapes, allowing them to be embedded into flexible and deformable wearable devices. [29][30][31][32] Furthermore, it is possible to fabricate robots with a relatively small weight and volume as they present a power density comparable to the skeletal muscles. [33] Neverthe...

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Section: Discussionmentioning

confidence: 99%

Soft Wearable Rehabilitation Robots with Artificial Muscles based on Smart Materials: A Review

Gonzalez-Vazquez

Garcia

Kilby

et al. 2023

Advanced Intelligent Systems

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“…The benchmarking for the actuator speed using the proposed variable length method was performed by applying a linear chirp signal [32]. It consists of a sinusoidal sweep signal that varies its frequency over time, which can be expressed as follow:…”

Section: Chirp Responsementioning

confidence: 99%

Improved performance in temperature and speed of TCP artificial muscles for soft wearables robots by length modification

González

Garcia

Kilby

2023

Smart Mater. Struct.

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Artificial muscles provide a unique solution for wearable rehabilitation robots (WRRs) because they are compliant, compact, and lightweight. Twisted and coiled polymer actuators (TCPs) are artificial muscles from thermally activated polymer fibres. They present high power density, linearity, stress and strain compared to other artificial muscles. Nevertheless, as TCPs require heat to start, their main barrier for widespread use in WRRs are their slow reaction times and the high temperatures they reach. Previous studies have analysed different parameters, like fibre material, fibre diameter, and various cooling systems, to improve TCP frequency response and working temperature. Nevertheless, the length of the actuator has not been explored as a possible parameter to enhance the actuation performance in this regard. This work focuses on studying the behaviour of TCPs with different lengths and how the performance in frequency response and temperature can be improved using the length as a primary parameter, as they are critical for wearable robots. First, a characterisation of the TCPs was performed. Then, a method to improve frequency response, based on offsets on long actuators was implemented and validated using a chirp signal. The experimental results show that the mechanical characteristics are similar regardless of the actuator’s length. They reached a strain of 10 % with a power of 0.16 W/cm. However, the electrothermal properties changed as the power needed to increase temperature was higher when the actuator was enlarged. Therefore, an improvement in the required temperature was found, able to reduce the temperature with the same frequency response. Regarding the technique to enhance the speed of the actuator, it was possible to increase the frequency by 0.0006 Hz for each mm applied as an offset. Hence, the frequency response for the same displacement was increased linearly as the actuator was elongated.

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“…Indeed, control accuracy depends not only on the robot dynamics (which may include undesired nonlinear effects) but also on the unknown environment dynamics, which may critically affect performance and stability [1][2][3]. To shed light on this kind of issue, the benchmarking of force control algorithms has been recently investigated [4][5][6][7]. Although issues due to the interacting environment have been recognized by the robotics community, it is quite surprising that existing works on force control benchmarking have not adequately addressed them [5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

“…To fill this gap, our research team-as part of the EUROBENCH project [10]-has recently developed the Forecast framework: a benchmarking methodology and tools able to assess the performance of different force control algorithms while considering the importance of the interacting environment [4,11]. Such tools include (a) a simulation framework, (b) an affordable and modular hardware testbed, (c) a low-level control framework to control the testbed and (d) a high-level graphical user interface.…”

Section: Introductionmentioning

confidence: 99%

Environment Aware Friction Observer with Applications to Force Control Benchmarking

Dimo,

Calanca

2024

Actuators

Self Cite

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The benchmarking of force control algorithms has been significantly investigated in recent years. High-fidelity experimental benchmarking outcomes may require high-end electronics and mechanical systems not to compromise the algorithm’s evaluation. However, affordability may be highly desired to spread benchmarking tools within the research community. Mechanical inaccuracies due to affordability can lead to undesired friction effects which in this paper are tackled by exploiting a novel friction compensation technique based on an environment-aware friction observer (EA-FOB). Friction compensation capabilities of the proposed EA-FOB are assessed through simulation and experimental comparisons with a widely used static friction model: Coulomb friction combined with viscous friction. Moreover, a comprehensive stability comparison with state-of-the-art disturbance observers (DOBs) is conducted. Results show higher stability margins for the EA-FOB with respect to traditional DOBs. The research is carried on within the Forecast project, which aims to provide tools and metrics to benchmark force control algorithms relying on low-cost electronics and affordable hardware.

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Benchmarking Force Control Algorithms

Cited by 5 publications

References 5 publications

Soft Wearable Rehabilitation Robots with Artificial Muscles based on Smart Materials: A Review

Soft Wearable Rehabilitation Robots with Artificial Muscles based on Smart Materials: A Review

Improved performance in temperature and speed of TCP artificial muscles for soft wearables robots by length modification

Environment Aware Friction Observer with Applications to Force Control Benchmarking

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