Search for: All records

Many robotic tasks rely on physical interactions with the task environment. Sensing when and where links make physical contacts can be crucial in several applications, including but not limited to grasping, locomotion, collaborative robotics and navigation. While sensorizing robot end effectors with intrinsic tactile devices is a logical approach, current and accessible options are often expensive or require invasive modifications. This paper presents a prototype method of both sensing and localizing contacts along a rigid link that can be readily incorporated into existing machines. The mechanism is lightweight and low-cost, and functions by actively providing an oscillatory mechanical actuation signal to a rigid link, whose mechanical response is measured with an inertial device and is used to localize touch at one of five designated contact points. Classification is performed with supervised methods using transient behavior and spectral features. Evaluation is conducted with five-fold cross validation, and preliminary results indicate promising performance in localizing the point of contact on the rigid link with accuracy of over 97%. 

Haptic feedback can render real-time force interactions with computer simulated objects. In several telerobotic applications, it is desired that a haptic simulation reflects a physical task space or interaction accurately. This is particularly true when excessive applied force can result in disastrous consequences, as with the case of robot-assisted minimally invasive surgery (RMIS) and tissue damage. Since force cannot be directly measured in RMIS, non-contact methods are desired. A promising direction of non-contact force estimation involves the primary use of vision sensors to estimate deformation. However, the required fidelity of non-contact force rendering of deformable interaction to maintain surgical operator performance is not well established. This work attempts to empirically evaluate the degree to which haptic feedback may deviate from ground truth yet result in acceptable teleoperated performance in a simulated RMIS-based palpation task. A preliminary user-study is conducted to verify the utility of the simulation platform, and the results of this work have implications in haptic feedback for RMIS and inform guidelines for vision-based tool-tissue force estimation. An adaptive thresholding method is used to collect the minimum and maximum tolerable errors in force orientation and magnitude of presented haptic feedback to maintain sufficient performance.