| Supported by the project entitled "The scientific basis of bio-mechatronics on human motor function reconstruction" from the National Basic Research Program (973) of China (Grant No.2011CB013300) and by the project entitled "The research on flexible tactile sensitive element of artificial skin and microcontact printing process" from the National Natural Science Foundation of China (Grant No.51105333), the design and manufacturing technology of distributed flexible capacitive tactile sensor for artificial prosthesis were studied in this thesis. Firstly, the materials utilized for forming the distributed flexible capacitive tactile sensor were chosen and its structure which was investigated by finite element analysis was designed. Secondly, the sensor was fabricated and the experiments were conducted for measuring its static and dynamic performance. The electric stimulation feedback experiment was carried out to realize the tactile feedback function of artificial prosthesis. Finally, the multipoint detection system was developed and an improved version of distributed flexible capacitive tactile sensor was designed and fabricated. Then, a series of experiments were carried out to study the performance of the improved sensor.In chapter1, the background and significance of this research was introduced. Then, the current research situation about artificial prosthesis and flexible tactile sensors was expatiated, and the research contents of the thesis were proposed.In chapter2, the distributed flexible capacitive tactile sensor based on PET and PDMS was designed. The sensor was made up of surface bump layer, top plate layer and bottom plate layer. The nonlinear stress-strain relationship and Young’s modulus under small deformation of different mass ratio PDMS were acquired through uniaxial tension and compression testing experiments. Then, the sensor was investigated by COMSOL software and the line-structure dielectric layer was analyzed and discussed.In chapter3, the lift-off method was carried out to deposit copper layer followed by spin coating15μm thick20:1PDMS film to fabricate top and bottom plate layers. The7.5:1PDMS surface bump layer was manufactured by replica molding the aluminum mold twice. Then, the oxygen plasma was used to treat the bonding surfaces and the three layers were assembled on a mask aligner. The sensor had the characteristics of bright color and good flexure capacity. In chapter4, the experimental platform was established. The static characteristic curve indicated that the sensitivity could be0.55‰/mN in the measuring range of0-200mN and be0.025‰/mN between300and800mN. The response time was about60ms through the loading and unloading circles. Then, the tactile signal feedback system including a myoelectric prosthesis, the tactile sensor, an operational amplifier circuit and an electric stimulator was set up to realize tactile feedback function which showed good accuracy and speediness.In chapter5, the scanning circuit system for multipoint detection was designed. The schematic and circuit board were developed and the program for controlling the MCU was accomplished.In chapter6, an improved tactile sensor which contained a line-structure dielectric layer was designed and fabricated, its spatial resolution could be2mm. The static and dynamic performance experiments were conducted, the results showed the sensor had excellent characteristics consisting of dual measuring ranges, high sensitivity, sensation of light force, good repeatability, low hysteresis, and the response time was less than60ms. Then, the color images of pressure mapping and force value were illustrated from the varied test blocks pressing experiments. This method was utilized in grasping and pinching of the prosthesis which demonstrated the achievement of tactile sensation capability.In Chapter7, the chief work of this thesis was summarized, and the future research objects were presented. |
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