ELECTRICAL & ELECTRONICS PCB-MOTION CONTROLLERS
INMOCO
Build or buy a three-axis motion controller ?
Three-axis embedded PCB motion controllers are integral for applications such as robotic arm control . While high volume and specific development needs might drive towards an in-house build , minimising development time and lowering cost for smaller volumes is an advantage of buying-in a controller . Comparing these approaches , a hybrid option can also offer the best of both worlds .
Gerard Bush of motion specialist INMOCO compares the build versus buy approach for PCB-motion controllers .
Printed Circuit Board ( PCB ) -based motion controllers are frequently integrated within applications such as laboratory automation , mobile robotics , test equipment , packaging machines , and robot arm control . Typically controlling three axes of brushless DC and / or stepper motors up to around 350W , the increasing trend is to embed a microchipbased controller within the machine itself . The close proximity this provides enables faster response times , less noise , and a more compact footprint , plus a reduced cabling .
While cost can be saved compared to highvolume procurement , the design effort for developing a three-axis motion controller PCB is significant .
Selecting connectors and the wiring scheme is a preliminary step , and this stage can take up to three months . Next , a pivotal decision is the approach to the motor amplifier . A designed-from-the-ground up amplifier offers the greatest flexibility in specification and control . However , with design considerations such as electromagnetic interference and current control , this process is likely to take at least three months or more . Instead , an off-the-shelf PCB-mounted amplifier can be integrated , still providing advanced features such as safety controls , while saving development time .
The other primary component decision is the motion control chip itself . Using a separate micoprocessor gives the freedom to write a customised motion engine code . This affords complete flexibility over motion functions , but development would add at least 12 months to the project . To enable communication with the host network and coordinate motion
Balancing specification requirements with cost , an OEM faces the decision of procuring an established controller or developing their own . Assuming an off-the-shelf controller can meet needs , development volume that impacts the total procurement cost might be the deciding factor . Alternatively , an exacting specification might drive internal development . While examining the pros and cons of both approaches , a hybrid option can combine the best of both worlds .
BUILDING A CONTROLLER
The advantages of developing in-house are two-fold . Firstly , this approach gives a controller that is entirely tailored to the application in terms of connectors and form factor , as well as dedicated functionality . Unique design can also be a selling point , providing it includes features that the market is willing to pay for . The other main advantage is cost . Assuming the production run is high enough , talking in the region of 1,000 units or more , a custom designed controller might be a more costeffective procurement option .
The clear requirement , however , is the need for expertise and time in development .
70 PECM Issue 60