‘I can hear it buzzing in the air tonight …’ Ok, so I took a little poetic license with the lyrics of Phil Collins’ classic hit ‘In the Air Tonight’, but it made for a more interesting opener than ‘Hi, my name is…’. What is this guy droning on about you may be asking. Sit tight…
Our new Kinetis V series of ARM® Cortex®-M class MCUs has set embedded motor control in a new direction. Our motor control demo vault is filled with a vast array of industrial and appliance type creations as those have historically represented the biggest slice of the motor control pie. While such demos have performed admirably for many years and continue to do so, we thought that it was time to look further afield for an application befitting of our first ARM-Cortex-M7 based MCU. Motor control is after all, the largest consumer of electricity on the planet so presumably there must be an unknown talent out there just waiting for its turn in the spotlight.
After many hours of coffee and doughnut fuelled deliberations, the demo team settled on a drone. Why drones? The short answer is “because washing machines don’t fly very well”. No, in all seriousness there are a number of reasons why the drone, UAV or quadcopter was deserving of its place. Firstly, it ticks the ‘cool’ box. Defying gravity is always a neat trick but it now comes with added flair with drones now able to perform all types of aerial wizardry. Secondly, spinning multiple motors accurately is a task that our Kinetis V series MCUs take in their stride so it showcases the MCU’s talents to good effect. Technical prowess box ticked. Thirdly, is the potential business opportunity associated with it. What began as a hobbyist play-thing is now rapidly transitioning into a viable commercial market of sizeable proportions and increasingly diverse end applications. These magnificent “men-less” flying machines are finding new destinations on an almost daily basis including aerial surveying of structures and farmland, cargo transportation to remote communities, and even shark spotting in California. The market is still at an embryonic stage with many regulatory hurdles to clear, but all the signs are that it won’t be long before drones will be delivering pizza to your house (hopefully not dumped on your roof ‘Breaking Bad’ style). In short, this application is….wait for it…..taking off.
4 x 8-bit MCU = 1 x 32-bit Kinetis V MCU
When it comes to motor control, our expertise is par excellence. Naturally I’m biased, but decades of new product development, turn-key customer projects for the industry’s ‘big players’, and a vast library of sophisticated enablement software speaks for itself. With that in store and Kinetis V series MCUs ‘straining at the leash’, the drone demo project was seized upon. Against an aggressive schedule – typical of every trade show demo request from marketing I expect – the development team was set in motion. Motor control passions were ignited and soon propellers would (hopefully) begin turning.
The drone selected was the DJI Phantom1 – a workhorse of the market and hence a suitable platform with which to test our V series MCU’s credentials. Propeller guards were also purchased to avoid any unfortunate finger incidents – 8K rpm blades can cause quite a nip.
The Embedded Speed Controller (ESC) modules were the target area – four per drone and each controlled by one 8-bit 8051 MCU. A new consolidated ESC design was manufactured using one KV5x ARM Cortex-M7 MCU where previously there had been four 8-bit MCUs. Leveraging the MCU’s agile performance and highly integrated motor control peripherals – 240MHz ARM Cortex-M7 core, high resolution PWMs, multiple high speed ADCs (5Msps) and its inter-peripheral crossbar – a four off 6-step BLDC control system was implemented. This required approximately 50% of the KV5x MCU’s CPU performance leaving additional bandwidth to implement field oriented control (FOC) and flight stability control functions in future ESC designs.
An additional KV4x ARM Cortex-M4 version of the ESC was built to demonstrate the unique scalability that the Kinetis V series brings to this and countless other motor control applications. One MCU family – multiple end products, with scalable form, functionality and price.
By coincidence, the demo team discovered a parallel drone project using a new gate driver IC. A quick decision was made to join forces and include the GD3000, adding further power control capability while replacing several additional discrete components. More BOM cost reduction. With schematics drawn up, PCBs populated and software tested, the result was 2 new custom made ESC modules, and thankfully no missing fingers.
Up, up and away
The Kinetis V series drone made its maiden flight recently. Unfortunately, for logistical/safety/legal reasons, drones can’t be flown freely in such built up areas (hotels owners aren’t keen on drones ‘buzzing’ their elaborate ballroom chandeliers), hence it was temporarily caged it within a safety cabinet. However, it won’t be long before it’s fully airborne and appearing on the Internet of Tomorrow tour trucks, training seminars and multiple other locations around the globe. So look out or should I say look up, for a Kinetis V series drone coming to a city near you soon.
It is often said that the best things in life are those that move us. While my pun-infused ramblings might not, I’m fairly confident that the Kinetis V series will. If not, try Phil