Research On Thermal Effect Variable Stiffness Mechanical Gripper Based On Triboelectric Tactile Sensing

Soft robots have become the focus of academic research in recent years.These robots have been widely used in industry,agriculture,military,medical and exploration fields.As a typical representative of soft robots,soft grippers have excellent flexibility and unique advantages in handling fragile and complex-shaped objects.However,such grippers have problems such as low load capacity,single movement form and poor control accuracy.To solve above defects,a series of solutions have been eliminated,while most of improvement difficult to take into account the soft gripper original mechanical properities.In addition,Complex structure makes these schemes hard be applied in practice.Based on thermoplastic materials’ modal transition principle and triboelectric sensor,a variable stiffness mechanical gripper is proposed in this paper.This gripper can adaptively grasp objects with different range of size and weight.The main research contents of this paper are as follows:(1)A fiber reinforced soft actuator was designed as the driving element of gripper’s finger and the structural parameters were optimized based on finite element simulation to improve the performance of actuator.The structure,working principle and manufacturing process of the actuator were introduced in detail.Combined with Yeoh constitutive model and uniaxial tensile experiments,accurate silicone material parameters were obtained.Analysed the impact on actuator bending performance caused by section shape,cavity thickness,and winding pitch.Determined actuator geometries considering the stability and bending property.Built the static model of actuator to obtain the relationship between bending angle with air pressure.(2)A variable stiffness module based on PLA material is designed to effectively improve the finger stiffness and realize multiple bending modes.The structure,working principle and manufacturing process of the variable stiffness module were introduced in detail.Analyzed the impact on performance of stiffness caused by hole shape,aperture and layout.Analyzed the effect of line layout on response speed.Built experimental platform to test the finger performance under the variable stiffness module.Established kinematic model to determine the workspace under different bending modes.(3)A high sensitivity triboelectric tactile sensoring unit based on single motor mode is researched and designed,which can be compatible with soft finger to adapt to large deformation.The structure,working principle and manufacturing process of the sensing unit were introduced in detail.The influence of contact pressure,contact frequency,contact material,working temperature and humidity on signal output is determined through experiments to characterize the output characteristics of the sensoring unit.In addition,the stability of the sensoring unit is verified by 2000 cyclic contact experiment.(4)Based on the above research,the system of gripper was built.The mechanism and hardware composition of system were introduced.Working process and principle of self-adaptive grasping were described in detail.Comprehensive evaluation of gripper performance from radial and tangential grip performance.Through a series of general grasping tests and space operation,verified the practicability and universality of soft gripper.