Constant-force mechanisms can be used for gravity counterbalance and force regulation. While many constant-force mechanisms have been designed, most of them have a limited range of force adjustment, which brings very limited capability to maintain an equilibrium state when load changes. In this paper, a novel design of reconfigurable constant-force mechanism is proposed. The new design is inspired by a variable stiffness mechanism, which can work in a similar way as the hinged lever, but take a compact space. Moreover, the design allows to adjust the configuration parameters achieving a large range of the equilibrium state adjustment. Mathematical models are developed to simulate the equilibrium performance changed with configuration parameters. A prototype is constructed and validates the working principle of the design. A design case is included to show the application of the mechanism in a passive assistive upper-body exoskeleton.
TianYZhouCWangF, et al. Design of a flexure-based mechanism possessing low stiffness and constant force. Rev Scientific Instr2019; 90(10): 105005.
3.
PhamH-TWangD-A. A constant-force bistable mechanism for force regulation and overload protection. Mechanism Machine Theor2011; 46(7): 899–909.
4.
WangPXuQ. Design of a flexure-based constant-force XY precision positioning stage. Mechanism Machine Theor2017; 108: 1–13.
5.
ZhouLLiYBaiS. A human-centered design optimization approach for robotic exoskeletons through biomechanical simulation. Robotics Autonomous Syst2017; 91: 337–347.
6.
ZhouLChenWChenW, et al. Design of a passive lower limb exoskeleton for walking assistance with gravity compensation. Mechanism Machine Theor2020; 150: 103840.
7.
GullMABakTBaiS. Dynamic modeling of an upper limb hybrid exoskeleton for simulations of load-lifting assistance. Proc Imeche, C: J Mech Eng Sci2021; 0(0): 1–14.
8.
BoyleCHowellLLMaglebySP, et al. Dynamic modeling of compliant constant-force compression mechanisms. Mechanism Machine Theor2003; 38(12): 1469–1487.
9.
NaharDSugarT. Compliant constant-force mechanism with a variable output for micro/macro applications. IEEE International Conference on Robotics and Automation, 14. Taipei, Taiwan, 2003. 318–19323.
10.
LanCCWangJHChenYH, et al. A compliant constant-force mechanism for adaptive robot end-effector operations. In: IEEE International Conference on Robotics and Automation. USA; 2010. 2131–2136.
11.
WangPXuQ. Design and modeling of constant-force mechanisms: a survey. Mechanism Machine Theor2018; 119: 1–21.
12.
PedersenCBWFleckNAAnanthasureshGK. Design of a compliant mechanism to modify an actuator characteristic to deliver a constant output force. J Mech Des2005; 128(5): 1101–1112.
13.
NathanRH. A constant force generation mechanism. J Mech Trans Auto Des1985; 107(4): 508–512.
14.
KazerooniHKimS. A new architecture for direct drive robots. In: IEEE International Conference on Robotics and Automation. Philadelphia, PA, USA; 1988. 442–445.
KimSNussbaumMAMokhlespour EsfahaniMI, et al. Assessing the influence of a passive, upper extremity exoskeletal vest for tasks requiring arm elevation: Part II - “Unexpected” effects on shoulder motion, balance, and spine loading. Appl Ergon2018; 70: 323–330.
17.
PacificoIScanoAGuanziroliE, et al. An Experimental Evaluation of the Proto-MATE: A Novel Ergonomic Upper-Limb Exoskeleton to Reduce Workers' Physical Strain. IEEE Robot Automat Mag2020; 27(1): 54–65.
18.
RahmanTSampleWJayakumarS, et al. Passive exoskeletons for assisting limb movement. J Rehabil Res Dev2006; 43(5): 583–590.
19.
HyunDJBaeKKimK, et al. A light-weight passive upper arm assistive exoskeleton based on multi-linkage spring-energy dissipation mechanism for overhead tasks. Robotics Autonomous Syst2019; 122: 103309.
LiuYLiZBaiS. Design of a reconfigurable novel constant-force mechanism for assistive exoskeletons. In: 5th IFToMM Symposium on Mechanism Design for Robotics. France: Futuroscope-Poitiers; 2021. 1–10.
25.
LiZBaiS. A novel revolute joint of variable stiffness with reconfigurability. Mechanism Machine Theor2019; 133: 720–736.
26.
PlagenhoefSEvansFGAbdelnourT. Anatomical data for analyzing human motion. Res Q Exerc Sport1983; 54(2): 169–178.
27.
de LevaP. Adjustments to Zatsiorsky-Seluyanov's segment inertia parameters. J Biomech1996; 29(9): 1223–1230.
28.
ZhouLBaiS. A new approach to design of a lightweight anthropomorphic arm for service applications. J Mech Robot2015; 7(3): 031001.
29.
ZhouLChenWWangJ, et al. A novel precision measuring parallel mechanism for the closed-loop control of a biologically inspired lower limb exoskeleton. IEEE/ASME Trans Mechatron2018; 23(6): 2693–2703.
