Error Source Identification in Measuring Soft Tissue Stiffness and Self Compensating This Error Using Three Probes Configuration

摘要

One of the biggest challenges for measuring soft tissue stiffness using tactile sensors is to have an output independent of the contact conditions. Although the approach of using two springs with different stiffness is used, the output of sensor is usually unstable because of the soft tissue surface irregularity. This irregularity creates an inclination angle between the sensor tips and the tissue. By scanning some real organs of a chicken using laser microscope, it is found that the angle value does not exceed 3 degrees. A modification on the original sensor is proposed to compensate that error. A finite element analysis for the two sensors is carried out to compare their behavior. The error of the original approach is about 55% and 103% with an inclination angle 3 degrees on the left and right direction, respectively. However, the modified sensor output is stable up to 8 degrees with an error not exceeding 4%. Furthermore, it could differentiate between different soft tissues stiffness within the specified range.