Non-Contact Temperature Sensing Using Resonance Frequency for the Robotic Arm with LMPA Joints

In this paper, we propose a temperature sensing method for the robotic arm with low melting point alloy (LMPA) joints. In the Fukushima Daiichi Nuclear Power Station (F1NPS), the decommissioning plan is in progress. To remove the debris safely and certainly, the monitoring of the radiation in the pedestal is needed. For this task, we proposed a highly expandable robotic arm system using low melting point alloy (LMPA) at all joints. Each joint of the arm can switch between free and fixed states using the phase state change of LMPA. In order to operate the arm system efficiently, the joint temperature must be sensed to recognize the phase state of the LMPA. We focus on the resonance frequency of the LC resonance circuit as a temperature sensing method. The LMPA is heated though heating plates by induction heating (IH) method. The resonance frequency of the LC resonant circuit built in the IH device varies according to the temperature of the object to be heated. Measuring the oscillating frequency of IH device and the temperature of the heating plates, we confirmed that they correlated linearly around the melting point of LMPA and the usefulness as the temperature sensing method.