Controller for linear actuators in medical equipment - Page 1
Forum section: electronics / projects

author: Jonas N
author_rank: Newbie
timestamp: June 15, 2018, 01:48:29 pm
content: Hello, I just got into this forum after watching some of the awesome youtube videos from EEVblog for a while.I don't feel too good about asking for advice the first hour I join the forum, but hopefully I can contribute with my knowledge in the future.Introduction:I'm working on medical equipment for helping elderly in their homes and institutions, and the ongoing project is to implement some automatic functions to a motorized chair. I have no experience in manufacturing electronics and my relevant knowledge is mostly theory (pen and paper electronics from my cybernetics education), robotics, software and hobby microcontrollers. The tech development team is currently only me, which is why a system designed from scratch is probably not a good idea. The team will be strenghtened in the future, but probably not before this first model is released. Yes there is only me with technical background (cybernetics and robotics), in addition to a couple of product designers and a bunch of sellsmen.Product:The chair will have three linear actuators that set the position of the chair's modules (height, tilt and back). The user should be able to control the actuators individually, but software should also control these actuators automatically with help from sensors (accl. gyro, force, etc.). The system must be flexible such that one actuator (and corresponding functionality) can be removed if the user doesn't need it. The actuators are typically 24 V and max 2-10 A, with position feedback. The first model should be ready in about a year. The estimated sales is between 100-500 the first year, so it's not about a mass production to begin with.What I have done so far:For an early stage prototype to test functionality I used an Arduino Uno together with a relay board (drawing current from 24V battery) to get sensor inputs and to control the actuators. This works OK, but is not suitable for manufacturing of course. I've found some off the shelf control boxes that are sertified as medical equipment, which would make this a lot easier. The problem is that those have very limited functionality, no digital or analog inputs and I can not write code on them. Those are mainly plug an play with a hand controller. E.g.http://www.reac.se/products/control-systems/rcb10/Question:In my opinion there is three alternatives, and I hope some of you can help me with choosing the right alternative and put me on the right track of where to go from here.1: Use a controller that can handle this functionality and is certified as medical equipment - This is the best option for the first model, but I haven't found one of these yet2: Use a less advanced controller (like the one from Reac) together with a microcontroller or self developed circuit to handle the sensors and software.3: Develop the circuit and motor controller from scratch.(4): Outsource parts of the work.I would love to learn about the process from prototype to a manufactured product, but the chair will be released in about a year from now, which is not much time to do this by myself with limited experience in addition to the long process of prototyping, testing, and getting the system certified for medical equipment.Thank you very much for taking the time to look at this, any advice would be helpful!

author: Benta
author_rank: Super Contributor
timestamp: June 15, 2018, 03:16:38 pm
content: If you haven't chosen your actuators yet, get in touch with Linak in Denmark. They're experts in this field and deliver actuators for hospital beds etc. They can also help you with the required interlocks (so you don't crush the patient).No affiliation.

author: SiliconWizard
author_rank: Super Contributor
timestamp: June 15, 2018, 04:40:52 pm
content: I second that, Linak has great products, and you'll find both actuators and controllers, and I'm sure they can help with your project.They even have a subsidiary in Norway (LINAK Norge AS):http://www.linak.no/

author: max_torque
author_rank: Super Contributor
timestamp: June 15, 2018, 05:02:48 pm
content: The first thing you need to do if to find out what legal requirements your system MUST meet and which requirements you would like to meet (for your own peace of mind / company reputation) In general, after aerospace, the medical arena is one of the most heavily regulated industries for very good reason!

author: Jonas N
author_rank: Newbie
timestamp: June 18, 2018, 06:37:41 am
content: Thanks guys, I will for sure check out Linak!