Research on Soft Robot Design for Grasping and Climbing Scenarios


Student thesis: Doctoral Thesis

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Awarding Institution
  • Dong SUN (Supervisor)
  • Erbao Dong (External person) (External Supervisor)
  • Jinjin Zheng (External person) (External Supervisor)
Award date30 May 2022


Soft robots have shown great potential in compliant grasping and climbing due to their simplicity, compliance, and safe interaction, thus having become a research hotspot in the field of robotics recently. However, soft robots still encounter problems such as limited environmental adaptability in grasping and climbing scenarios. Among them, soft grippers can grasp objects of different shapes or stiffness due to their compliant structure, but they lack strong adaptability and high grasping force to different surface environments under low power consumption. Soft climbing robots use soft grippers as feet modules and can achieve safe and efficient climbing, but they still lack strong motion capability in various surface environments. Traditional soft robots are based on soft materials such as silicone, which can maintain high deformability with low modulus. However, they often lack structural programmability, stability, and load-bearing capacity during grasping and climbing. This thesis aims to address these challenges of soft robots in different application scenarios from the following three aspects.

First, a soft gripper integrating flat dry adhesive, soft actuator, and microspine is proposed to improve the comprehensive grasping ability of the soft gripper on smooth and rough surfaces. The flat dry adhesive and soft actuator are integrally cast and fabricated, and a retractable microspine structure is anchored at the end of the gripper. The dry adhesive has strong adhesion on smooth surfaces. The soft actuator made of shape memory alloy wires can enable the compliant deformation of the gripper. The microspine has strong adhesion on rough surfaces and can retract and protrude under the action of shape memory alloy coils. The results show that the soft gripper can provide large grasping force on regular or irregular objects with smooth or rough surfaces. To further lower the power consumption of the soft gripper and avoid the overheating of shape memory alloy actuators, a soft gripper design with self-locking joints is proposed to perform long-time and high-load grasping tasks with low power consumption. Inspired by a ratchet wrench, the self-locking joint incorporates a ratchet mechanism that provides a high grip force via mechanical interlocking. The results show that the gripper can grasp objects with a high payload-to-weight ratio and hold them without consuming power.

Then, a soft climbing robot is developed based on the modular design idea, addressing the adaptability and motion capability in variable surface environments. Feet modules with different adhesive strategies, such as magnetics, negative pressure, dry adhesion, and microspine, are designed and fabricated, which can work in combination with soft body modules actuated by shape memory alloy wires. The results show that the soft climbing robot can provide strong adhesion on different surfaces and exhibit strong motion capability on flat and non-planar surfaces with different properties, such as smooth or rough.

Finally, soft origami robots with high-modulus materials are developed to improve the structural stability and load capacity of soft robots, which can achieve large shape deformation via compliant folding. Furthermore, an inverse origami design model is proposed to automatically generate the flat crease pattern of the desired origami structure. With this model, various programmable soft robots, such as soft climbing origami robots, vacuum-actuated origami muscles, and miniature soft origami grippers, can be quickly developed to achieve grasping and climbing functions.

In summary, this thesis provides new ideas and technical references for solving the challenges of soft robots such as environmental adaptability in grasping and climbing scenarios through innovative structural design.

    Research areas

  • Soft robotics, Soft gripper, Soft climbing robot, Soft origami robot