Linear Guides for Refreshable Braille displays

Linear guides are extensively employed in several industrial applications. Miniaturization, minimal friction, cost efficiency and low maintenance are the major challenges faced while developing a linear motion system. My task was to design an energy efficient linear guide for latching mechanism in refreshable braille display (link 1, link 2) developed at IIT Delhi, India.

Following were the requirements:

  • Single degree of freedom
  • The two different latch part should not interfere
  • Size should not be more than 20mm X 68mm
  • Capable of handling eccentric loads

(Aug. 2016 - Nov. 2016)

Metal Bush Sliding Guide

Hole and slot mechanism

Four bar mechanism

Linear ball guideway

In order to find an efficient solution, I started exploring different types of linear guides. Using kinematic design principles, I designed and analyzed seven different types of linear guides. Out of these seven designs, four are traditional contact-based designs whereas the other three are complaint mechanisms based design. Following are the seven mechanisms:

  1. Metal Bush Sliding Guide: two rods slides inside two holes.
  2. Hole and slot mechanism: two rods sliding in a hole and a slot.
  3. Four bar mechanism: the Latch part is attached to the coupler.
  4. Linear ball guideway: Metal balls are inserted between two parts in motion.
  5. Orthoplanar spring based mechanism: the latch part is attached to an orthoplanar spring.
  6. Hole flexure-based mechanism: parallel movement achieved through hole flexures.
  7. Parallel sheet flexure: parallel motion achieved through combination of two sheets.

I used numerical methods, Finite Element Method (FEM), as well as testing of fabricated prototypes to compare the efficiency of these mechanisms. Parallel sheet flexure, owing to its frictionless motion, resulted in 87% reduction in power consumption. The detailed analysis of these mechanisms was published in ASME 2017 (IDETC/CIE) conference (doi:10.1115/DETC2017-68311).

Orthoplanar spring

Hole flexure

Parallel sheet flexure

Testing of Linear ball guideway

Testing of Parallel sheet flexure