Inexpensive DC Series and ACIM ASIC controllers, no uC, DSP or programming
Hi everyone. I have noticed a trend towards the use of DC series traction motors in DIY EV projects.
In this thread I am going to design an inexpensive, very basic, easy to build
but also efficient DC series motor controller with modern ASICs,
based on PWM control of the applied DC voltage and hysteretic control of the maximum motor current.
Why? I'm going to buy an EV for daily use, building one is mainly for the fun of it.
I don't have a lot of spare time or money to spend on it, so a DC traction conversion is the best option for the next couple of years.
A drivetrain based on a DC series motor is by far the easiest and least expensive way to get traction (high start-up torque) from a DC power source.
As demonstrated in a recent video of a €1000 build and in every ICE car with a DC series starter motor.
DC series motors have been used for propulsion for ages and back in the pre-IGBT era,
torque and speed of DC series motors were controlled by shifting a tap on a huge, high power series resistor bank.
Very inefficient of course, but that is the way it was done when I was EE student in my first year.
At the core, the driver of the vehicle is the most important part of the control mechanism,
being both the feedback path and the input. A very elegant control solution because of its simplicity.
In the design in this thread the resistor bank will be replaced with modern silicon in ASICs.
Yes, application specific integrated circuits, so there's no time consuming complexity from microntrollers,
digital signal processors, unnecessary and potentially unstable controllers (PID) in software and the biggest issue: bugs and programming errors.
The electronics only kick in automatically when the response of the driver is too slow for the protection of the power electronics and the motor: overcurrent protection.
That is what "very basic" means, but it takes very little effort to dress up the controller with whatever (automated) (protection) feature is wanted.
Examples: cruise control, monitoring (warning lights, gauges), reduction of the maximum motor current when there's not enough air flow across the cooler.
The schematic shows the heart of the controller: only three SOT-23 devices, the lvc4066 and the lvc14 can be replaced with a single lvc3157 SPDT device.
Current sensing for overcurrent protection is done with a low cost LEM sensor.
Hysteretic control is implemented with a low cost comparator (MCP6561) and a LTC6992 has a suitable frequency response for the conversion of the throttle input into a PWM signal for the power stage.
EDIT: The all hardware ACIM controller is introduced later on. Thanks again, Damien!
AC STUFF HAS BEEN GREAT RETRO FUN.
PLEASE HAVE A LOOK AT MY BASIC (TESLA) ACIM MICROCONTROLLER PROJECT THREAD.
IT WILL SOON BE RELEASED ELSEWHERE OPEN SOURCE.