1530-437X (c) 2016 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/JSEN.2016.2640199, IEEE Sensors Journal 1 Abstract—This paper investigates the effects of gamma radiation on the operation of commercially available capacitive microelectromechanical (MEMS) accelerometers intended for use in robotic systems deployed for nuclear disaster remediation. Radiation-induced accelerometer degradation is examined in terms of its effects on the input-output relationship of ADXL325 accelerometers (Analog Devices, Inc., Norwood, Massachusetts, USA) prior to sensor failure. Results show a moderate increase in sensor nonlinearity as well as significant, non-monotonic changes to accelerometer axis sensitivity and zero-g bias. Both part-to-part variation and axis-to-axis variation within individual accelerometers are observed. The effects of the observed accelerometer degradation on the performance of a simple robotic manipulator that relies on acceleration feedback is evaluated in simulation. Additionally, using tools derived from adaptive control theory, this paper presents a real-time recalibration technique for mitigating the effects of the measured accelerometer degradation on the performance of robotic systems that can be applied in-field, without knowledge of the degradation mechanisms. An example implementation of this technique is also evaluated. Results suggest that control-based strategies for mitigating hardware degradation may be able to extend the useful operating lifetime of non- radiation-hardened sensors in robotic systems deployed in extreme radiation environments. Index Terms—Accelerometers, adaptive control, gamma radiation, radiation effects, robotic sensing, total ionizing dose I. INTRODUCTION leanup efforts following the 2011 disaster at the Fukushima-Daiichi Nuclear Power Station in Fukushima, Japan, are estimated to last 40 years and cost a total of $15 billion (USD) [1]. The potentially extreme radiation levels occurring in post-nuclear-disaster environments such as Fukushima necessitate robotic intervention to protect human workers from unacceptable health risks during both emergency and long-term disaster response. However, radiation-induced degradation of robot sensors and other components can also 1 Corresponding author This work was supported by the U.S. Defense Threat Reduction Agency Basic Research Award # HDTRA1-13-1-0011 to Vanderbilt University. E. B. Pitt and E. J. Barth are with the Department of Mechanical Engineering, Vanderbilt University, Nashville, TN 37212, USA. Email: {bryn.pitt, eric.j.barth}@vanderbilt.edu. Z. J. Diggins, N. Mahadevan, G. Karsai, B. D. Sierawski, R. A. Reed, R. D. Schrimpf, R. A. Weller, M. L. Alles, and A. F. Witulski are with the Department have deleterious effects on the performance of robotic systems. The incident in Fukushima has demonstrated a clear need for the development of mobile robots capable of performing reconnaissance, rescue, and remediation tasks in an extreme radiation environment [2], [3], [4]. Radiation-induced sensor degradation compromises a robot’s perception of its environment, which in turn potentially compromises its ability to navigate and perform useful work on its environment. Long before a sensor’s output ceases to correspond to its input (i.e. sensor “failure”), radiation-induced changes to the input-output relationship can lead to diminished, unacceptable performance in robotic systems [5]. Previous research on the effects of total ionizing radiation dose (TID) on semiconductor devices has shown that the input-output relationship of sensors varies with TID [5], [6], [7], [8], followed by sensor failure with increasing TID. In recent years, accelerometers based on microelectromechanical (MEMS) technology have become a common, low-cost, option for high-bandwidth acceleration measurements in a wide range of robotic applications, in particular applications in mobile robotics and robotic manipulation, which generally emphasize minimizing size, weight, and power consumption. MEMS devices have also been found to withstand very high levels of radiation prior to failure, making them particularly well-suited for use in extreme radiation environments (see [9] for a review of relevant literature). However, analyzing radiation effects on MEMS accelerometers is somewhat more complex than traditional semiconductor devices, given that the sensors often consist of both a mechanical transducer element and support electronics fabricated together in single monolithic package. (Note that in the context of robotics, the term “sensor” does not typically refer to the transducer alone but rather to the entire sensor system, including support electronics. This convention is used in this paper.) Radiation-induced failure mechanisms for electrostatic MEMS accelerometers reported in the literature of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, TN 37235, USA. Email: {zachary.j.diggins, nag.mahadevan, gabor.karsai, brian.sierawski, robert.reed, ron.schrimpf, robert.a.weller, mike.alles, arthur.f.witulski}@vanderbilt.edu. E. Bryn Pitt 1 , Eric J. Barth, Member, IEEE, Zachary J. Diggins, Member, IEEE, Nagabhushan Mahadevan, Gabor Karsai, Senior Member, IEEE, Brian D. Sierawski, Senior Member, IEEE, Robert A. Reed, Fellow, IEEE, Ronald D. Schrimpf, Fellow, IEEE, Robert A. Weller, Senior Member, IEEE, Michael L. Alles, Member, IEEE, and Arthur F. Witulski, Senior Member, IEEE Radiation Response and Adaptive Control- Based Degradation Mitigation of MEMS Accelerometers in Ionizing Dose Environments C