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工程设计学报
Chin J Eng Design  2023, Vol. 30 Issue (2): 262-270    DOI: 10.3785/j.issn.1006-754X.2023.00.028
Basic Parts Design     
Design and performance analysis of reconfigurable variable stiffness compliant actuator
Weijie DUAN1(),Huibin QIN1(),Rong LIU1,Zhongyi LI2,Shaoping BAI3
1.School of Mechanical Engineering, North University of China, Taiyuan 030051, China
2.Hangzhou Innovation Institute, Beihang University, Hangzhou 310051, China
3.Department of Materials and Production, Aalborg University, Aalborg 9220, Denmark
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Abstract  

Compliant actuators can achieve safe interaction between robots and humans due to their inherent flexibility, and have strong environmental adaptability. To meet the requirements of exoskeleton robots for joint flexibility and variable stiffness characteristics, a reconfigurable variable stiffness compliant actuator was designed, which could achieve reconstruction by changing the geometric parameters, materials and quantity of elastic components, and achieve variable stiffness within an adjustable range by adjusting the radial preload. Firstly, based on the transmission principle of a zero-length frame four-bar mechanism, a stiffness mathematical model of the variable stiffness compliant actuator was established, and the influence of the number of flexible branches and the stiffness and preload of elastic components on the output torque and stiffness of the actuator was analyzed. Then, an ADAMS virtual prototype model of the actuator was established, and the statics performance simulation analysis was carried out to verify the correctness of the stiffness mathematical model. Finally, the dynamics model of the actuator was established and the transfer function of the dynamics system was obtained through Laplace transform. The frequency characteristics analysis results indicated that the stability of the compliant actuator was good. The designed compliant actuator had a small volume and small mass, which could be applied in the driving mechanism of wearable exoskeleton robots. The research results provide theoretical and technical references for the design of compliant driving joints in robots.

Key words： compliant actuator      reconfigurable      variable stiffness      dynamics model     
Received: 23 September 2022      Published: 06 May 2023
CLC:  TH 122  
Corresponding Authors: Huibin QIN     E-mail: dwjttt@163.com;qhbsss@163.com
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Weijie DUAN
Huibin QIN
Rong LIU
Zhongyi LI
Shaoping BAI
Cite this article:

Weijie DUAN,Huibin QIN,Rong LIU,Zhongyi LI,Shaoping BAI. Design and performance analysis of reconfigurable variable stiffness compliant actuator. Chin J Eng Design, 2023, 30(2): 262-270.

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https://www.zjujournals.com/gcsjxb/10.3785/j.issn.1006-754X.2023.00.028     OR     https://www.zjujournals.com/gcsjxb/Y2023/V30/I2/262


可重构变刚度柔性驱动器的设计与性能分析

柔性驱动器因其固有的柔顺特性，能够实现机器人与人之间的安全交互，且具有较强的环境适应能力。为满足外骨骼机器人对关节柔性及变刚度特性的要求，设计了一种具有可重构性的变刚度柔性驱动器，可通过改变弹性元件的几何参数、材料和数量来实现重构，通过径向调节预紧力来实现可调范围内的变刚度。首先，运用零长度机架四杆机构的传动原理，建立了变刚度柔性驱动器的刚度数学模型，分析了柔性分支数和弹性元件刚度、预紧力对驱动器输出扭矩和刚度的影响规律。然后，建立了驱动器的ADAMS虚拟样机模型，并开展静力学性能仿真分析，验证了刚度数学模型的正确性。最后，建立了驱动器的动力学模型，通过Laplace变换得到了动力学系统的传递函数。频率特性分析结果表明，该柔性驱动器的稳定性良好。所设计的柔性驱动器体积小且质量小，能够在可穿戴外骨骼机器人驱动机构中应用。研究结果为机器人柔性驱动关节的设计提供了理论和技术参考。


关键词： 柔性驱动器,  可重构,  变刚度,  动力学模型 
Fig.1 Explosion view of variable stiffness compliant actuator
Fig.2 Internal view of variable stiffness compliant actuator
Fig.3 Variable stiffness principle of a compliant branch
Fig.4 Principle of radial adjustment of preload
参数数值
l0/mm80
l1/mm10~20
l3/mm34
ke/(N/mm)2.0
N3
θ/rad-1~1
Table 1 Structural parameters of variable stiffness compliant actuator
Fig.5 Variation of output torque of variable stiffness compliant actuator with deflection angle and preload
Fig.6 Variation of stiffness of variable stiffness compliant actuator with deflection angle and preload
Fig.7 Variation of elastic potential energy of variable stiffness compliant actuator with deflection angle and preload
参数数值
直径/mm2
密度/(kg/mm3)1.0×10-6
弹性模量/(N/mm2)50.955
刚度比1
初始载荷/N7.5
阻尼比0.02
Table 2 Parameter setting of elastic components in ADAMS software
Fig.8 Comparison of variation curves of output torque with deflection angle of variable stiffness compliant actuator
Fig.9 Dynamics model of variable stiffness compliant actuator
参数数值
负载等效转动惯量Ip/(kg·m2)1.784×10-3
电机等效转动惯量Im/(kg·m2)1.1×10-7
减速器等效转动惯量Ig/(kg·m2)6×10-8
VSM等效转动惯量Ivsm/(kg·m2)3×10-5
负载阻尼系数Bp/(Nms/rad)—
电机阻尼系数Bm/(Nms/rad)3.96×10-6
VSM阻尼系数Bvsm/(Nms/rad)0.02
负载质量mp/kg0.080 43
电机输出力矩Tm/Nm—
VSM输出扭矩Tp/Nm—
负载连杆长度lp/m0.062 26
减速器传动比i1∶63
减速器效率η0.7
Table 3 Dynamics parameters of variable stiffness compliant actuator
平均刚度Ka/（Nm/rad）特征方程的根
2-5.605±33.432j
5-5.605±52.908j
10-5.605±74.846j
Table 4 Roots of transfer function of dynamics system of variable stiffness compliant actuator
Fig.10 Nyquist diagram of dynamics system of variable stiffness compliant actuator
Fig.11 Bode diagram of dynamics system of variable stiffness compliant actuator
Fig.12 Digital prototype and physical prototype of wearable compliant actuator elbow joint
Fig.13 Compliant actuator elbow joint wearing test site
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