Adi Bonen

A novel electrooptical proximity sensor for robotics: calibration and active sensing

An electrooptical proximity sensor capable of measuring the distance and two-dimensional orientation of an objects surface is presented. The robustness of the sensor, targeted for utilization in robotic active sensing, is achieved via the development of a novel amplitude-modulated-based electrooptical transducer, an electronic-interface circuit that provides very good noise immunity and a wide dynamic operating range, and an effective multi-region calibration process that significantly improves pose-estimations at near proximities. An experimental setup was designed and implemented for the development and verification of the proposed proximity sensor in a simulated robotic environment. Experimental results using a variety of calibrated surfaces and materials are presented and discussed. It is shown that average accuracies of 0.01 mm and 0.03/spl deg/ can be achieved. The robustness of the proximity sensor is also verified for potential use in grasping objects with a priori noncalibrated surfaces.

Distributed-force recovery for a planar photoelastic tactile sensor

In this paper, an efficient force-recovery algorithm is presented for a novel planar photoelastic tactile transducer. A distributed-force profile input to the tactile sensor developed in our laboratory generates stress in the photoelastic layer of the transducer, making it birefringent. Circularly polarized light input to the transducer is elliptically polarized at the output due to phase-lead created in the stressed photoelastic layer. The algorithm presented recovers the phase-lead distribution and correlates it to the input force profile. Since this distribution is a linear function of the force profile, the solution of the inverse-tactile problem is significantly simplified. The paper presents the analytical basis of the algorithm as well as the numerical technique used in its solution.

Finite-element analysis for photoelastic tactile sensors

In this paper, a photoelastic tactile transducer is modelled and analyzed using finite-element analysis (FEA). The effects of both normal and tangential forces are considered. Two different boundary conditions are examined for a transducer whose compliant protective layer has different mechanical properties from the photoelastic layer.

Phase-lead reconstruction of a photoelastic tactile sensor

In this paper, a novel tactile photoelastic transducer for normal forces is presented. When a normal input force profile is applied to the tranduction medium, stress is generated in the photoelastic layer making it birefringent. Consequently, circularly-polarized input light becomes elliptically polarized at the output due to the introduction of a phase-lead distribution. If a circular-reflection polaridoscope is used, the output light-intensity is a circular function of the total phase-lead distribution. The first part of the paper describes the forward analysis of the transducer using finite-element analysis to determine the stress distribution in the transducer. Then, the phase-lead distribution is determined using the theory of photoelasticity. The second part of the paper describes a technique for the recovery of the phase-lead distribution from the ideal noise-free light-intensity distribution. Also, a verification method is proposed to determine whether a recovered phase-lead distribution is the correct one or not. In the third part of the paper, we consider the nonideal situation, where the light-intensity distribution is no longer noise-free. Quantization errors added to the detected light-intensity distribution are also considered. Recovering the phase-lead distribution under noisy conditions constitutes an ill-posed problem. An algorithm that accurately and effectively determines the phase-lead distribution from a noisy light-intensity distribution is presented. The inverse-tactile problem is solved using an optimization function.

Development of a robust electro-optical proximity sensor

The development of a robust fiber-optic proximity sensor is presented. A method is proposed by which to solve the problem of robustness of amplitude- and phase-modulated electrooptical proximity sensors to variations in surface-reflection characteristics, and to reduce the influence of distance and orientation measurements on one other. The method comprises three different methodologies, which are combined for better efficiency: integration of distance and orientation sensors, a novel polarization-based optical-filtering approach, and active sensing. Emphasis is given to unique solutions for background-noise interference and dynamic-range-limitation problems.