FEATURE Drives, Controls & Motors
To build or buy a motion controller for your project?
Gerard Bush of motion specialist INMOCO compares the build-versus-buy approach for PCB-motion controllers T
hree-axis embedded printed circuit board (PCB) motion controllers are integral for applications such as laboratory automation,
mobile robotics, test equipment, packaging machines and robot arm control, among others. Whilst high volume and specifi c development needs might drive towards in- house build, minimising development time and lowering cost for smaller volumes is an advantage of buying-in a controller. Here, a hybrid option can also off er the best of both worlds. Typically controlling three axes of
brushless DC and/or stepper motors up to around 350W, the increasing trend is to embed a microchip-type controller within the machine itself. The close proximity this provides enables faster response times, less noise and a compact footprint, plus reduced cabling.
Building a controller
The advantages of developing in-house are two-fold: First, this is a tailored approach, giving the controller dedicated functionality, specifi c to the application, with specifi c connectors and form factor. The second advantage is cost: when producing volumes of thousands of units, a custom-designed controller can be cost-eff ective. However, in-house design requires expertise and time. Selecting connectors and the wiring scheme is the fi rst step, a stage that can take up to three months. Next is the design of the motor amplifi er. If done from the ground up, an amplifi er can be made fl exible in specifi cation and control. Its design will also involve considerations such as electromagnetic interference and current control, a process that can set you back least another three months. Instead, an off -the-shelf PCB-mounted amplifi er can be integrated, still providing advanced features such as safety controls, while saving on development time. Then there’s the motion control chip itself. Using a separate microprocessor gives the freedom to write a customised motion engine code, but this stage can add at least 12 months to the project. To enable communication with the host
24 April 2023 | Automation
network and coordinate motion sequences, the microprocessor will need software development, taking up to six months. As with the amplifi er, an off -the-shelf motion control chip can be integrated into a custom- designed PCB controller to save time, yet retain control over its form factor, profi le generation and fi eld-orientated control. Then, the PCB schematic stage
requires research, selection and testing of components. Integrating the control chip and amplifi er, the latter would also require a dedicated circuit, which could add yet another 12 months or so. The fi nal aspect of the software development process is application and motion parameter development, requiring a timespan of up to 16 months.
All in all, with a potential development needing up to 58 months, divided into a three-person team the project can take up to 18 months or more.
Buying in a motion controller Most of these steps can be removed by using a ready-to-go PCB-based motion controller. Development time can shrink to over a year, and doesn’t necessarily mean a sacrifi ce in motion control features. As well as functionality such as profi le and servo position control, integrating user- downloadable code written with C language libraries also extends their control fl exibility. An advantage of buying in an off -the-shelf motion controller is that it can also be more cost-eff ective if a lower volume is required.
Quicker development also means faster time to market. Demands of end users and the competitive landscape might make this the preferable approach, even for higher volume projects.
The hybrid approach
OEMs can also choose to use a hybrid approach that features PCB-mounted motion control modules. These single-axis modules can handle up to 1kW and can execute user-written application software, extending control fl exibility. Just like an off -the-shelf controller, these modules include advanced motion functions such as profi ling, fi eld-orientated control and safety, and are easy and fast to integrate. Mounted on a user-designed, application- specifi c interconnect board, these modules require much simplifi ed wiring, needing just connectors and capacitors.
Like the buy-in option, the engineering
resources required are signifi cantly lower. Following simplifi ed hardware integration, engineers can move directly to application development. This approach however still lets the OEM create a controller within their own form factor. Given the right volume, procurement cost of the hybrid approach can also return a lower rate than the buy-in option.
CONTACT:
INMOCO
www.inmoco.co.uk
automationmagazine.co.uk
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