I'm currently mechanising the prototype of my scaled up flexible robot arm (commonly called a spine robot).

I began by using three motorised slide potentiometers as pseudo linear actuators to control the arm's tendon cables, but quickly found that even by maxing their motors out with a not-recommended 12V they did not provide enough torque. The arm's tendons need to be pulled/pushed at least 1-3cm to move the gripper end of the arm a substantial distance, and the motorised sliders were not cut out for the job.

I've moved onto using a home-made servo controlled 2-axis gimbal plate. Movement of the arm is achieved by tilting each axis in a coordinated way to lengthen and shorten each of the three tendon cables attached to its triangular top plate.

Not only do the servos generate more torque via the gimbal plate, they are also considerably easier to control by using the included Arduino servo class. As shown in my example code, I've written a basic function to map a set of predetermined x,y coordinates to degree positions on the servos. This means I can string multiple function calls together to generate more complex programs in the future.

Here's a bonus video of the arm running the example code