Prof. J. Walter - Informationstechnik, Mikrocomputertechnik, Digitale Medien Concept Development
Hochschule Karlsruhe Logo Microcontroller Technology
Intelligent Crutch

3.9 Concept Development

An iterative design process has been chosen to develop the whole system. At the beginning, the first goal is to obtain raw weight and accelerometer sensor data from two crutches as fast as possible. This data will then be analized for feasability and to develop algorithms to detect and accurately calculate the critical limb load while walking:

Data Flow
Figure 3.9.1: General concept of the intelligent crutch.

Develpment will take part in the following two parts:

1. Test setup with reduced functionality:
Equip two crutches simple and fast with microcontrollers, weight sensors, accelerometers and batteries in form of breakout boards. Synchronize measurements by pounding both crutches together and searching for a peak in acceleration data. Send raw sensor data from both crutches to android device. Show synchronized data from both crutches and export it into one .csv-file for further analysis.

2. Fully functional prototype:
Construct a fully functional prototype with direct feedback for patient and GUI for medical personnel. Design and fit PCB with electrical components. Shrink down mechanical design accordingly.

To realize an efficient solution, a normal crutch will be modified. The original upper part is unchanged. The lower inner tube will be modified. It will still be possible to adjust the crutch length in the usual way. The first step of mechanical development is mounting the weight sensor. This must be done in a way that axial load is transfered unchanged to the weight sensor while every lateral load is absorbed by the crutch tube.

Sketch Sensor Position
Figure 3.9.2: Design concept of the intelligent crutch.

A first sketch of a possible mounting position of the FX1901 force sensor. The crutch tube is closed at the bottom, so it can deliver force into the center bump of the force sensor. The main foot-unit can be 3D-printed in TPU, a high-strength, slightly flexible material.
Depicted in black is a linear bearing, possibly an aluminium tube. It takes the side forces, which are created by the torque of setting the crutch foot on its edge, which happens in use. It still allows linear movement without significant friction, so the force sensor can get accurate readings. In the final design, the opening on top must allow the assembly of the sensor into the main foot unit.

The following pictures show CAD design for the test setup. Alle electric components are housed inside a 3D-printed box.

test setup 1  test setup 2  test setup 3
Figure 3.9.3: Mechanical Design of the intelligent crutch.

Electrical components will be integrated inside crutch tubing for the final prototype:

Figure 3.9.4: Electrical components integration

  With Support of Prof. J. Walter Summer Semester 2021