Transcutaneous Control Of Implantable Electric Joint

Implantable electric joint system, which controls the rotation of the implanted electric knuckle according to the neural consciousness signals, can realize some functions of palm so as to improve the self-care ability of palm-paralysis patients. One of the key technologies of implantable electric joint system is transcutaneous transmission of power for motor drive and signal for motor control.The transcutaneous power transmission system, which is based on the principle of electromagnetic induction, can achieve great power transmission. In the power transmission system, a power amplifier drives the transmitting coil in vitro and an implanted coil receives power resonantly in vivo. Since transcutaneous power transmission system is applied to human body, it requires high efficiency of power transmission to decrease the possibility of the tissue damage caused by overheating and to improve portability.In this paper, we use a class-E amplifier to drive the transmitting coil in the transcutaneous power transmission system, for the theoretical efficiency of class-E amplifier is 100%. According to the design equations of class-E amplifier, we have analyzed the relationships between the output power and the input voltage. Combining the secondary circuit, we have proposed the design methodology of transcutaneous power transmission system with a class-E amplifier. By analyzing the functional relationship between the loss of each component and the duty cycle of driving signal, we have reached a conclusion that the system efficiency can be improved by increasing the input voltage and the duty cycle.Fast and stable signal transmission is the prerequisite to achieve precise control for implanted electric knuckle. Combining design equations of class-E amplifier, we have offered the methodology of transcutaneous signal transmission with a class-E amplifier. Modulating input voltage is used to transmit signals from in vitro to in vivo, and modulating impedance is used to transmit signals from in vivo to in vitro. Envelope detection is used to demodulate signals in both of these two signal transmission methods. Since the class-E amplifier will deviate from the optimum state when signals transmit from in vivo to in vitro, it is difficult to get the modulation depth. Therefore, Pspice simulation has been used to determine modulation depth in this paper.Based on the theory of transcutaneous power and signal transmission, a transcutaneous power and signal transmission system has been designed to realize the transcutaneous control of implantable electric joint system. Two lithium batteries connected in series supply power for system so as to improve endurance and input voltage, which can improve transmission efficiency. In the implantable electric joint system, there is a small AVR microcontroller in primary and secondary circuits respectively. In primary circuit, the microcontroller detects neural consciousness signals to control power and signal transmission. In secondary circuit, the microcontroller receives command signals to control the rotation direction of implanted electric knuckle.