The ability to climb greatly increases the reachable workspace of terrestrial robots, improving their utility for inspection and exploration tasks. This is particularly desirable for small (millimeter-scale) legged robots operating in confined environments. This paper presents a 1.48-gram and 4.5-centimeter-long tethered quadrupedal microrobot, the Harvard Ambulatory MicroRobot with Electroadhesion (HAMR-E). The design of HAMR-E enables precise leg motions and voltage-controlled electroadhesion for repeatable and reliable climbing of inverted and vertical surfaces. The innovations that enable this behavior are an integrated leg structure with electroadhesive pads and passive alignment ankles and a parametric tripedal crawling gait. At a relatively low adhesion voltage of 250 volts, HAMR-E achieves speeds up to 1.2 (4.6) millimeters per second and can ambulate for a maximum of 215 (162) steps during vertical (inverted) locomotion. Furthermore, HAMR-E still retains the ability for high-speed locomotion at 140 millimeters per second on horizontal surfaces. As a demonstration of its potential for industrial applications, such as in situ inspection of high-value assets, we show that HAMR-E is capable of achieving open-loop, inverted locomotion inside a curved portion of a commercial jet engine.

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Precise radio based positioning for low power wide area networks remains a challenging research area due to narrowband signals and multipath propagation. Multi-channel ranging provides improved temporal resolution by coherent processing. While this technique has been applied to short range radio standards, no experimental demonstration for long range radio devices exists. The present paper introduces a hardware testbed for phase coherent multi-channel processing of narrowband signals. Simulations and preliminary experimental multi-channel results show a higher ranging precision (factor 20) over time based ranging. In a frequency flat channel with a 10 kHz signal, precisions down to 10 m (phase based) and 200 m (time based) have been achieved. Precision degrades in multipath propagation scenarios.

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Current fabrication methods for lithium-ion batteries impose a limit on how light a high power battery can be made. The lack of lightweight (< 300 mg), high power batteries is a significant constraint to the development of untethered micro-robots, wearable haptics, mobile computing, and biomedical applications. We have developed a laser micro-machining and assembly process which can produce batteries up to 30 times lighter than the lightest high power commercial cell, at comparable power densities (> 1 kW/kg). Our process is versatile and can be adapted to make custom geometries, miniature high voltage cells, and more, all while using a broad range of starting materials. We see this technology as a path to highly versatile miniature power sources, that will enable a wide range of small-scale applications.Existing fabrication technologies cannot be used to make lightweight, high power density lithium-ion batteries (< 300 mg). The need is increasing for these small, powerful batteries, as advances in fabrication techniques push the limits of miniaturization in robotics, [1] haptics, [2] wearable and biomedical technologies, [3] and mobile computing for the Internet of Things. [4] Unfortunately, current fabrication methods for lithium-ion cells force the end user to make a choice between high energy density and lightweight batteries (Figure 1(a)). Supercapacitors can provide even higher power density (> 10 kW/kg), but have very short discharge times (0.1-5 s), which limits the range of potential applications. [5] To push the limits of performance, we have developed a hybrid manufacturing approach which uses commercially available lithium-ion materials and a laser micro machining method to build lightweight (10-200 mg) high power density (> 1 kW/kg) batteries.Miniaturization of Li-ion batteries is limited by how the fabrication processes scale down, [5,6] Conventional Li-ion electrodes are made as planar films that are stacked into prismatic or cylindrical shapes. The stacked electrodes are infused with electrolyte, then sealed into a metallized film pouch, which prevents moisture from infiltrating into the battery. The materials and processes used to prevent moisture infiltration take up a significant amount of total battery weight, and scale unfavorably as the size of the battery is reduced. Furthermore, most nickel and aluminum commercial tabs weigh hundreds of milligrams, and need large areas for reliable welding to the electrodes. For high power devices, tabs and welds need to be oversized to avoid excessive resistive heating during fast charge or discharge. While several devices have been demonstrated to deliver high power at very small-scale (1-100 mg), the fabrication processes are either long duration, [7] or rely on unconventional materials, [8] or are difficult to replicate. [9] In addition, the most established processes to make lightweight batteries rely on thin-film, solid electrolyte chemistries, which suffer from rate limitations at room temperature, [10,11] To create lighter mesoscale power sources,...

Accurate range estimation with narrowband low power radio devices is challenging due to limited signal bandwidth and high frequency offsets of low-cost oscillators. The present paper provides new results concerning the Cramer Rao bounds of narrowband ranging systems applying a multi-channel coherent processing approach. Particularly, compared to existing literature, oscillator frequency offsets and multipath influence are taken into account. By numerical simulation it is shown, how the radio channel frequency selectivity degrades the ranging precision. Finally, a few guidelines for the design of new long range low-cost ranging systems are provided.

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Accurate radio signal based geolocalization for Low Power Wide Area networks is a key-enabler to various Internet of Things applications. However, localization with narrowband signals remains challenging in multipath environments. Sequential coherent multi-channel ranging improves temporal resolution while being compatible with narrowband transmissions. New radio chipsets integrate proprietary ranging functions. This paper compares a proof-of-concept implementation for coherent multi-channel ranging with narrowband signals to the Time-of-Flight ranging function of the LoRa 2.4 GHz radio chip. Benchmarking results for different configurations and propagation scenarios are discussed, illustrating the precision scalability of multi-channel ranging.