| The new generation of dexterous prostheses are able to satisfy most of the daily life grasping movements.However,the performance is far from a human hand and the abandon rate of myoelectric prosthesis is high.One of the key reasons is that there are no effective sensory closed loop in current commercial prosthesis.In this thesis,we developed a prosthetic sensory feedback system to detect and send the tactile and proprioceptive feedbacks to the user.We built this device in order to let an amputee to get information from his prosthesis hand without looking at it.The whole contents of this thesis can be divided into three parts.The first one is how to detect the data needed(force applied,distance between fingers,softness of the grasped object).The second one is how to encode these information,and the last one,how to send them to the subject.We used a force sensor to get the force applied.We took flex sensors to get the distance between fingers.With the data obtained from these sensors,we calculated the softness of the material grasped by observing the variation of distance between fingers after reaching the object.An Arduino managed the signals and triggered a STG4008 to send 8 type of transcutaneous stimulation(TENS)to the user,through a matrix of 5 electrodes.Twenty able-bodied subjects were recruited to test our system.The test results indicated that there was a learning process.They also underline a success rate converging to 94% for the softness detection,with a mean reaction time around 1000 ms.For the distance between fingers discrimination,the average success rate is 87,5% with a mean achievement time of 1000 ms.For the force detection,the discriminate rate was only 61%.With this thesis,we highlighted that we could detect and send information of distance,force and softness to a subject through TENS with a matrix of five electrodes.An acceptable discrimination rate of four kinds of diameters and three types of softness can be obtained.This system has the potential to be applied to intelligent prosthesis in the future. |
