Abstract
This paper presents an actuator control unit (ACU) with a 450-J embedded energy storage backup to face safety critical mechatronic applications. The idea is to ensure full operation of electric actuators, even in the case of battery failure, by using supercapacitors as a local energy tank. Thanks to integrated switching converter circuitry, the supercapacitors provide the required voltage and current levels for the required time to guarantee actuator operation until the system enters into safety mode. Experimental results are presented for a target application related to the control of servomotors for a robotized prosthetic arm. Mechatronic devices for rehabilitation or assisted living of injured and/or elderly people are available today. In most cases, they are battery powered with lithium-based cells, providing high energy density and low weight, but at the expense of a reduced robustness compared to lead-acid- or nickel-based battery cells. The ACU of this work ensures full operation of the wearable robotized arm, controlled through acceleration and electromyography (EMG) sensor signals, even in the case of battery failure, thanks to the embedded energy backup unit. To prove the configurability and scalability of the proposed solution, experimental results related to the electric actuation of the car door latch and of a robotized gearbox in vehicles are also shown. The reliability of the energy backup device has been assessed in a wide temperature range, from −40 to 130 °C, and in a durability test campaign of more than 10,000 cycles. Achieved results prove the suitability of the proposed approach for ACUs requiring a burst of power of hundreds of watts for only a few seconds in safety-critical applications. Alternatively, the aging and temperature characterizations of energy backup units is limited to supercapacitors of thousands of farads for high power applications (e.g., electric/hybrid propulsion) and with a temperature range limited to 70 °C.
Highlights
Mechanical systems in many safety critical applications such as vehicles and biomedical devices are becoming mechatronic systems with electric actuation
This paper has presented an electric actuation controller, where full operation is ensured, even in the case of battery failure, by using supercapacitors as a local energy tank
This paper has presented an electric actuation controller, where full operation is ensured, even in programmable converter circuitry, the supercapacitors provide the required voltage and current the case of battery failure, by using supercapacitors as a local energy tank
Summary
Mechanical systems in many safety critical applications such as vehicles (e.g., cars, trains, motorcycles) and biomedical devices (e.g., robotized prosthetic arms or legs to improve the quality of life of elderly, wounded, and disabled people with temporary or permanent handicaps) are becoming mechatronic systems with electric actuation The latter is controlled through embedded hardware-software electronic units [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]. The energy backup unit is optimized for safety-critical ACUs, providing a burst of hundreds of watts in only a few seconds, largely present in robotics and vehicular systems, and using supercapacitors of a few, or tens of, farads.
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