Topology Optimization for Design of a 3D-Printed Constant-Force Compliant Finger

Chih Hsing Liu, Fu Ming Chung, Yuan Ping Ho

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


A compliant constant-force mechanism is a passive force regulation device that can generate a nearly constant output force over a range of input or output displacements while without the use of sensors and feedback control. In topology synthesis of a compliant constant-force mechanism for a given input displacement range, the constant output force can be achieved by maintaining the output displacement to be nearly a same value while the input displacement increases. In order to further control the desired output displacement for the compliant constant-force mechanism before contacting the object, this article introduces a new composite objective function that can consider both the output force (with contact) and the output displacement (without contact) of the synthesized compliant mechanism. The sensitivity for the proposed objective function with respect to the element density is derived while considering the effect of nonlinearity in the large deformation condition. The proposed topology optimization method is used to design an innovative constant-force compliant finger, and its prototype is manufactured by 3-D printing using a flexible thermoplastic elastomer. The experimental results show the developed constant-force compliant finger can provide a nearly constant output force of 41.9 N over the input displacement ranging from 15 to 30 mm while the maximum and average force variations within the constant-force range are 2.2% and 0.9%, respectively. In addition, the developed constant-force compliant finger is used to design a three-fingered constant-force compliant gripper that can be used in robotic grasping of fragile objects.

Original languageEnglish
Article number9425015
Pages (from-to)1828-1836
Number of pages9
JournalIEEE/ASME Transactions on Mechatronics
Issue number4
Publication statusPublished - 2021 Aug

All Science Journal Classification (ASJC) codes

  • Control and Systems Engineering
  • Computer Science Applications
  • Electrical and Electronic Engineering


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