Determination of Contact Evolution on a Soft Hemispherical Probe Using Ultrasound

In the area of robotic sensing, determination of parameters of a solid object, such as contact area, pressure distribution, or deformation, is an important step for the sensing and manipulation of an object with an unknown mechanical behavior. In this paper, a soft contact probe based on ultrasound is developed using a commercial elastomer. The emphasis is placed on the study of the contact mechanics of the probe. The probe is equipped with an ultrasonic sensor and then implemented in a 3 degrees of freedom manipulator robotic system. The correlation between the normal contact force and the ultrasonic signal reflected from the interface between the soft probe and the object is precisely studied. Experimental results are presented for loading and unloading cycles of the soft contact probe against a flat surface. Tests are performed on aluminum, elastomer, and plasticine test samples. It is shown that the probe can potentially be used as an end effector of a robotic system which will use the recorded ultrasonic signal as the feedback to a force control algorithm.