Detection Of Finger Motion Gesture And Its Study On The Control Of Manipulator

The gesture of the finger movement reflects the motor function of the finger. The detection of finger motion gesture is an important means to evaluate motor function of the finger and provide reference data for the research on medical and sports bionics. The detection of finger motion gesture and analysing the discipline of the finger's motion can provide accurate and reliable reference for the study on the motion of the finger in the field of rehabilitation medicine, sports bionics, man - machine engineering and other fields.Based on the understanding of the detection methods on finger movement at home and abroad, we adopted the accelerometer to detect the movement gesture of the finger. On the basis of understanding the accelerometer'angle measurement principle, to verify the feasibility of the dynamic angle testing, a dynamic angle measurement experiment was conducted, and the results showed that the absolute error was less than 1.5 degrees in the static testing, whereas the absolute error and relative error mainly ranged of 1～2.5 degrees and 3%～6% respectively in the dynamic testing. On this basis, the sensors was used to measure the three joint angle changes during the index finger bending, and the dynamic camera system was employed to verify the accuracy by comparing the results measured by accelerometer and dynamic camera system, and the absolute error and relative error mainly ranged of 0.5～3.5 degrees and 2%～4% respectively; The accelerometer was further used to detect the kinematics information of the finger, such as angle, angular velocity and angular acceleration, and the results showed that the movement of three joints with both synchronization and differences. Then the accelerometer was used to detect the action of finger tapping the keyboard which was the finger's common action and the results was consistent with the report in relevant literature.Based on the verification experiment, the results measured by the sensor was applied to control the finger model. The finger model which has three freedom chose the stepper motor as the driving source by making use of the stepper motor's controllable rotation angle. The DSP TMS320F2812 internal 12-bit AD module was used to collect data of accelerometer which worn on the knuckle of index finger during the index finger bending, then the voltage signals from the sensor was converted into angle information, and then based on this angle information, the comparator module in DSP Event Manager (EV) sent the control pulse which corresponded with the angle information measured by the sensor. The motors drove the three knuckle model rotating the corresponding angle by sending the control pulse into motor drive module which was comsisted of L297 and L298 chips. Then the dynamic camera system was employed to detect the motion angle of the finger joint and the motion angle of the model joint. The error distribution was calculated by comparing the two results, and the absolute error mainly ranged of 0～3 degrees and the maximum absolute error was 5.5 degrees.This paper designed a simple three-finger manipulator according to finger size and range of motion of the human hand. The manipulator was consist of three modular fingers (thumb, index finger, middle finger) with each finger has three degrees of freedom and therefore, the manipulator has total of nine degrees of freedom. The manipulator was drived by the stepper motor and adopted the simple turbine and worm to transfer the force. The structure of the various parts of the manipulator were designed in mechanical drawing software Pro / E, and all the parts of the manipulator were processed and assembled according to the mechanical processing map. This paper achieved the further control on the manipulator by making use of accelerometer. The four sensors were placed in the corresponding position of palm, thumb, index finger, middle finger, and the Digital Signal Processor(DSP) was used to collect data of each accelerometer when the three fingers doing grasping movement, so the bending angle relative to the palm of the three fingers were detected and the angle information was used to control the manipulator so as to make the manipulator imitate human finger's movements. The motion velocity of the manipulator can be regulated by changing the frequency of the control pulse and the ideal frequency range of the control pulse was determined in the experiment.