Injection Buddy: An automated robot arm that performs injections

Jaclyn Canlas, Joshan Gill, Clara Lo, Alex Martinez and Lohita Swaminathan

Degree: Bachelor of Applied Science
Program:
- Integrated Engineering
Campus: Vancouver

Our project

We designed and built Injection Buddy, a robotic arm that administers subcutaneous injections for people with mobility challenges.

This device targets individuals with rheumatoid arthritis – who often have limited dexterity – who could use Injection Buddy to safely self-administer injections in the comfort of their own home.

Our design solution and process

Our automated five degree of freedom robotic arm performs injections for people who are unable or uncomfortable to do so themselves. The user places an arm cuff on for accurate landmarking, sits in a position with their shoulder facing the robotic arm and steps on a foot pedal to begin the arm movement. Injection Buddy then targets the injection site, moves into position and inserts the needle into the user’s arm, after which a linear actuator plunges the syringe to dispense the medication. The robot then moves back to its home position and the needle can be removed and disposed of.

Our device includes three arms; an electrical system that integrates power management, motor drivers, a microcontroller unit and encoder systems; and software that allows for locating the injection site and trajectory planning.

Putting together all these elements required each team member to focus on a specific area of expertise while communicating constantly with other team members and making adjustments as needed. For example, changes to an element of the mechanical design affected the vision system and how the vision system integrates with the electrical components.

Because it is difficult for cameras to visually detect a shoulder, we developed markers that are placed around the shoulder area. The vision system detects the centre of the marker, calculates its 3D coordinates and then determines a trajectory for the robot arm to get from home position to the shoulder and inject the syringe once it is in place.

After building the device and each part of the system from scratch – which required extensive design, machining, fabrication and assembly – we tested it for injection repeatability (whether it could consistently and accurately reach a predetermined position) and to see if it could reach a target pose based on vision-based input.

The challenges we faced

The fabrication of the arm and assembly took longer than expected. This created a time crunch later in the process – the longer it takes to set everything up mechanically, the less time you have to finetune the electrical and software systems.

We were working within a very tight budget to build our device. This challenge created an opportunity for us to be innovative in our approach.

For example, it’s common for robotic arms to use a stepper motor and gearbox to provide the torque needed to move the arm. But this combination of components is very expensive, costing around $120 per joint. Instead, we used a different type of motor and then added a component that – combined with our software – made the motor much more precise and provided the torque we needed at about $40 per joint.

What we’re most proud of

We built everything ourselves: we designed every joint, machined the parts and put it all together; created our own circuitry and built a custom control board capable of controlling six different motors simultaneously; and learned about vision systems and coded everything on the software side. This made it all the more meaningful when we got our device to work and repeatedly injected a syringe within a narrow radius.

We collaborated to solve problems and achieve full system integration. For example, there were times when the motors were not able to lift up the arm, and we had to work together to address mechanical and electrical issues.

We embraced a fluid and dynamic design cycle, and we were all committed to persevering to develop creative solutions to make our device the best it could be.

On the software side, after doing all the work on calculations, vision system, coordinate transformations, inverse kinematics and serial communication and testing it through simulations, it was very rewarding to see that work come to life and be translated into movement of the robotic arm.