Tactile Feedback Control System Capstone Project - Arduino code question


I am a student in biological engineering, working on my capstone project. The project aims to implement a tactile feedback system onto da Vinici surgical robotic system. (da Vinci is a surgical robot for minimally-invasive procedures) Currently, the da Vinci's arm that is manipulated by the surgeon receives no tactile feedback from the robotic arm (the arm that actually performs the surgery/contacts tissue and organs).

Our functional prototype consists of three parts: a strain gauge on the "robotic" arm, a linear servo (that controls the braking system) on the "master" arm, and an Arduino Leonardo board to connect everything together.

My question is about how to use the strain gauge voltage output to control the linear servo motor. The linear servo we are using is a Firgelli L12-R, a miniature servo motor controlled like a traditional R-C servo, using PWM control. For a pulse width of 1ms, the servo fully retracts and for a pulse width of 2ms, it fully extends (30mm). We will be applying varying forces to the robotic arm to get varying strains/output voltage values from the strain gauge. I want to use these values to command the linear servo to extend/retract different amounts. The ultimate goal is to calibrate the system such that for a given strain in the robotic arm, the force the arm experiences is equal in magnitude to the force that we are creating on the master arm (via a linear servo/elastic band braking system). What I mean is that I want certain voltage output ranges (from the strain gauge) to correlate with certain amounts of extension of the linear servo on the master arm.

Has anyone used a strain gauge to control a servo motor before? To create the master-robotic arm system, we used the potentiometer-servo code that is on the website. I was hoping to use the same code (with some modifications) for the strain gauge-linear servo system, where the strain gauge replaced the potentiometer.

Please let me know if you have any comments/questions/advice!

Thanks in advance!

Allie Cerutti

You need to provide more info or a data sheet link to the strain gauge to understand just how it operates.

Attached now are the datasheets/specs for the strain gauge, linear actuator, and the instrumentation amplifier (for the strain gauge)



omega strain gage datasheet.pdf (1 MB)

L12_datasheet.pdf (461 KB)

INA125P datasheet.pdf (363 KB)