To enable precise manipulation of fragile objects, robots need the sense of touch. Localized sensing of the 3D force vector with a few mN of resolution is desired. Magnetic force sensors, consisting of a magnet embedded in an elastomer and a 3D magnetometer, were demonstrated as desirable candidates. These prior-art sensors measure the local 3D magnetic field at a single sensing pixel. Hence, they cannot distinguish between the signal and stray magnetic fields. Any stray field directly leaks into the force readout signal path. This paper introduces a design immune to stray magnetic fields. The sensor uses multiple magnetic pixels, and operates on the gradient of the magnetic field. The pixels and conditioning electronics are fully integrated on chip. The 3D force calculation is based on a polynomial model fitted to a calibration data set. The impact of a 2-mT magnetic stray field on the force output is limited to 0.3% of the full scale-about two orders magnitude improvement over the prior art. The force resolution is 2.7 mN and remains competitive. Furthermore, an on-chip temperature sensor and an algorithm are used to compensate the intrinsic thermal drift in the range 0-50°C. To validate the proper force regulation in spite of a nearby magnet, we integrated our prototype into a robotic hand. Our results demonstrate the robustness of 3D magnetic force sensors in the presence of real-world parasitic disturbances.

Contactless magnetic position sensors are used in countless industrial and automotive applications. However, as a consequence of the electrification trend the sensors can be exposed to parasitic magnetic stray fields, and their desired robustness may be compromised. In this paper we publish for the first time how this challenge is addressed and constructively solved using a complete paradigm change leaving conventional magnetic field measurement behind and entering into the realm of magnetic field gradient measurement. Our novel sensor system consists of an integrated Hall sensor realized in 0.18 μm CMOS technology with magnetic concentrators and a four-pole permanent magnet. The intrinsic angular accuracy was assessed comparing the rotary position of the permanent magnet with the sensor output showing angle errors below 0.3°. Additional end-of-line calibration can be applied using built-in memory and processing capability to further increase the accuracy. Finally, we demonstrate the immunity against stray fields of 4000 A/m which led to errors below 0.1°, corresponding to 0.06% of the sensors fullscale angular range. In conclusion, this novel sensor system offers a compact and flexible solution for stray-field immune rotary position measurement in harsh environment.

We present a new Hall sensor design for the accurate and robust measurement of linear displacement. Implemented in CMOS, the sensor is based on a novel gradient measurement concept combining Hall elements with integrated magnetic concentrators. In typical applications with practical Ferrite magnets, the peak output voltage of the Hall transducers is only around 1.7 mV at the maximum operating temperature of 160℃, and thus requires high-performance low-offset readout electronics. Over its 15-mm linear displacement range, the sensor's total error is 1% including manufacturing tolerances, trimming accuracy, temperature, aging effects, and practical magnet constraints. In addition, the sensor is immune to magnetic stray fields up to 5 mT, complying with the most stringent automotive norm.

This paper experimentally demonstrates the stray-field robustness capability of a novel Hall-based rotary position sensor concept (Huber, S., et al, 2018). The sensor targets safety-related automotive applications, for example powertrain and power steering. In these applications, the safety requirement specifies a maximum stray-field induced error of 0.4°. Therefore, the robustness in corner cases needs to be assessed. We demonstrate the stray-field immunity in multiple corner cases for temperature from −40 °C up to 160 °C and over lifetime. The impact of a uniform 5 mT stray field over all conditions (3σ) is shown to be less than 0.25°. The fully-integrated automotive-qualified sensor is implemented in a 0.18-μm CMOS technology, and achieves 0.7° of angular accuracy.

We introduce a rigid analytification of the quantized coordinate algebra of a semisimple algebraic group and a quantized Arens-Michael envelope of the enveloping algebra of the corresponding Lie algebra, working over a non-archimedean field and when q is not a root of unity. We show that these analytic quantum groups are topological Hopf algebras and Fréchet-Stein algebras. We then introduce an analogue of the BGG category O for the quantum Arens-Michael envelope and show that it is equivalent to the category O for the corresponding quantized enveloping algebra.