A Current-Mode Analog Front-End for Capacitive Length Transducers in Pneumatic Muscle Actuators
Guido Di Patrizio Stanchieri,
Andrea De Marcellis,
Marco Faccio,
Elia Palange,
Michele Gabrio Antonelli,
Pierluigi Beomonte Zobel
Affiliations
Guido Di Patrizio Stanchieri
Electronic and Photonic Integrated Circuits and Systems Laboratory (EPICS Lab), Department of Information Engineering, Computer Science and Mathematics (DISIM), University of L’Aquila, Via Vetoio, Coppito, 67100 L’Aquila, Italy
Andrea De Marcellis
Electronic and Photonic Integrated Circuits and Systems Laboratory (EPICS Lab), Department of Information Engineering, Computer Science and Mathematics (DISIM), University of L’Aquila, Via Vetoio, Coppito, 67100 L’Aquila, Italy
Marco Faccio
Electronic and Photonic Integrated Circuits and Systems Laboratory (EPICS Lab), Department of Information Engineering, Computer Science and Mathematics (DISIM), University of L’Aquila, Via Vetoio, Coppito, 67100 L’Aquila, Italy
Elia Palange
Electronic and Photonic Integrated Circuits and Systems Laboratory (EPICS Lab), Department of Information Engineering, Computer Science and Mathematics (DISIM), University of L’Aquila, Via Vetoio, Coppito, 67100 L’Aquila, Italy
Michele Gabrio Antonelli
Industrial Automation and Mechatronics Laboratory (LIAM Lab), Department of Industrial and Information Engineering and Economics (DIIIE), University of L’Aquila, P.le Pontieri, Monteluco di Roio, 67100 L’Aquila, Italy
Pierluigi Beomonte Zobel
Industrial Automation and Mechatronics Laboratory (LIAM Lab), Department of Industrial and Information Engineering and Economics (DIIIE), University of L’Aquila, P.le Pontieri, Monteluco di Roio, 67100 L’Aquila, Italy
This paper reports on the design, implementation, and characterization of a current-mode analog-front-end circuit for capacitance-to-voltage conversion that can be used in connection with a large variety of sensors and actuators in industrial and rehabilitation medicine applications. The circuit is composed by: (i) an oscillator generating a square wave signal whose frequency and pulse width is a function of the value of input capacitance; (ii) a passive low-pass filter that extracts the DC average component of the square wave signal; (iii) a DC-DC amplifier with variable gain ranging from 1 to 1000. The circuit has been designed in the current-mode approach by employing the second-generation current conveyor circuit, and has been implemented by using commercial discrete components as the basic blocks. The circuit allows for gain and sensitivity tunability, offset compensation and regulation, and the capability to manage various ranges of variations of the input capacitance. For a circuit gain of 1000, the measured circuit sensitivity is equal to 167.34 mV/pF with a resolution in terms of capacitance of 5 fF. The implemented circuit has been employed to measure the variations of the capacitance of a McKibben pneumatic muscle associated with the variations of its length that linearly depend on the circuit output voltage. Under step-to-step conditions of movement of the pneumatic muscle, the overall system sensitivity is equal to 70 mV/mm with a standard deviation error of the muscle length variation of 0.008 mm.
