Hydraulic dildo

Overview
This article is refers to the use of a hydraulic system to provide erection and varying firmness and curvature of an artificial penis. Pressure feedback in the hydraulic system can also be used to sense insertion and the tightness of the orifice in which the dildo is inserted.

Anatomical Likeness
The erectile function of a human penis can be simulated with a hydraulic system consisting of a larger enclosuing tube with two smaller parallel tubes inside representing the corpus cavernosum. For a more acurate reproduction, a third tube still smaller can be added which represents the corpus spongiosum and also provides inflation to the end section which represents the glans. See for an anatomical picture

Hydraulic Details
Two seperate hydraulic systems are required, one which inflates the two corpus cavernosum and one which inflates the corpus spongiosum and glans. A peristaltic pump or screw driven syringe can provide the inflation force. Ordinary water could serve as the hydraulic fluid.