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Can someone more familiar with embedded design explain a bit more on this? Can this really turn cheap motors into industrial level motors suitable for hobbyists

Can someone more familiar with embedded design explain a bit more on this? Can this really turn cheap motors into industrial level motors suitable for hobbyists?

TFortunato 9y ago
I'm on a cell phone, so I'll be brief, but can add more detail later. I've been doing motor drivers and embedded work (software and electronics) for robotics for a while, and did work on motor driver ICs before that, so this is kind of my wheelhouse! Briefly: I can tell you that the electronics and software are only a few parts of the overall equation here. Yes, this does look like (from the demo video results), a decent driver design, however quality of the motor DOES matter, and will eventually become a limiting factor if you are lookig for high precision or high power, as you start to run into things like torque digging, motor heating, etc. There are also little things in the driver design that can bite you if you aren't careful, but I'd need to look at the schematics to comment. I'm not trying to crap on the project or designer. There was clearly some thought and care put into this! I just don't want people to expect magic, or to think that the only difference between an industrial servo and a hobbyist motor is the electronics. That said, you can get VERY far with good electronics and control software! A hobbyist project will probably do just fine with something like this (or a motor driver reference design from the chip manufacturers), and by the time they run into limits of those designs and hobbyist motors, they'll probably have a pretty good idea of where they need to go as a next step! I'll take a closer look at this design later, and update if anyone is interested.
- gvb 9y ago
  Please :-) Here are the documentation links to get you started: Hardware: https://github.com/madcowswe/ODriveHardware/ https://github.com/madcowswe/ODriveHardware/ v3.2 schematic: https://github.com/madcowswe/ODriveHardware/blob/master/v3/v3.2docs/schematic_v3.2.pdf https://github.com/madcowswe/ODriveHardware/blob/master/v3/v... Firmware: https://github.com/madcowswe/ODriveFirmware https://github.com/madcowswe/ODriveFirmware PC config and analysis support: https://github.com/madcowswe/ODrive https://github.com/madcowswe/ODrive FPGA: https://github.com/madcowswe/ODriveFPGA https://github.com/madcowswe/ODriveFPGA "... the FPGA logic and software that runs on the FPGA based ODrive. This is not currently in development, but may be resumed at some later date." ---- The hardware is based on a STM32F405RGT6[1] driving two TI DRV8301 brushless motor controller chips[2] and a bunch of MOSFETs to handle the power switching. I/O is a USB, CAN with driver chip, and SPI unbuffered on headers. [1] High-performance foundation line, ARM Cortex-M4 core with DSP and FPU, 1 Mbyte Flash, 168 MHz CPU, ART Accelerator http://www.st.com/en/microcontrollers/stm32f405rg.html http://www.st.com/en/microcontrollers/stm32f405rg.html [2] DRV8301 Three-Phase Gate Driver With Dual Current Shunt Amplifiers and Buck Regulator http://www.ti.com/lit/ds/symlink/drv8301.pdf http://www.ti.com/lit/ds/symlink/drv8301.pdf
  - carterehsmith 9y ago
    Sorry for being off-topic. I just want to say, "STM32F405RGT6" is possibly the most hardcore product/model name ever. Just beautiful.
    - revelation 9y ago
      There are usually a dozen variants of the same microcontroller design just with different peripherals, amount of memory, packaging.. You could just as well say STM32 or STM32F4 and that is pretty much 99.9% of the information you need to know :)
    - makomk 9y ago
      It packs a lot of information in. STM32F4 is ST Micro's range of high-performance ARM Cortex-M4 microcontrollers with FPU, STM32F405 is a particular family of devices in that range differing mainly in package and memory size, R specifies that it's the 64-pin variant, G indicates that it's the version with 1024KB of flash, T is the LQFP package, and 6 is for -40 to 85 °C temperature range. Most of this is shared across the entire STM32 range of devices.
tyingq 9y ago
I suspect there's no free lunch here. If they are designed for hobby r/c aircraft, they are designed for shorter runs with lots of free prop-driven fan cooling. Not for sustained runs without a prop cooling it. So, it would likely work, but have a shorter lifetime. The barrier to using them was having a low voltage / high current controller. This fills that gap. So, not a bad idea, but there's almost surely a durability tradeoff. And maybe that's fine for a hobbyist cnc application.
- TaylorAlexander 9y ago
  Cooling can be an issue if you drive them near their rated power without adequate cooling. And absolutely they won't have the same quality of construction as true industrial devices. However they are sufficiently powerful to be useful and cost effective at continuous duty levels below their max rated power.
- madcowswe 9y ago
  One thing to keep in mind is that for many robotics applications, the duty cycle for high torque (i.e. acceleration) is often quite low. So they may still run fairly cool.
analog31 9y ago
Historically, hobbyists have chosen stepping motors because they can be controlled with a fairly simplistic controller, and there are lots of solutions out there... check out some of the step motor drive boards at Pololu Electronics. But stepping motors have limitations, namely speed and torque per unit motor size. Note that as a hobbyist, I'm still living in the stepper motor world, so I'm interested in this project. Brushless servo motors offer the potential for much higher torque and speed in a small package, but require a different form of electronic control, and the gist of this project is that such controls haven't been available for hobbyists. So it's a matter of finding a gap in the existing project / product space, and filling it. Note that e-bikes use brushless servo motors, so somebody has done the math on what motor technology is most efficient. I also think these motors are in electric cars, and even appliances such as washing machines. I will be reading with interest. I'll also start keeping an eye out for what kinds of motors are available. As for "industrial level," I'd say that it's a matter of pushing machine speeds up to a level similar to what you might see in a factory. Often, with stepper motor driven gadgets, you accept the fact that your machine will take a long time to do anything, but who cares, it's a hobby. On the industrial side, you very quickly run into the situation where your motor is no longer the limiting factor affecting speed and precision, but the design and assembly of the mechanism is.
- TFortunato 9y ago
  Yeah, brushless is definitely the way to go for efficiency, and good smooth motion. Stepper for an e-bike or washing machine (Not a BLDC either, but...) would be nuts, and in general steppers are really for cheap semi-decent control, not for anything where precision is really needed.
  - TaylorAlexander 9y ago
    My colleague had a motor from a newer washing machine out on his desk, and it did appear to be a BLDC. Alternating magnets with three phases of coils as you'd expect. Driven from rectified 120V AC!
    - TFortunato 9y ago
bsder 9y ago
Sure, the issue with brushless motors isn't the motor, it's the encoder. The encoder is what "closes the loop" and allows you to get the accuracy you need. If you have a way to relate the position of the thing being controlled to the motor position, then you can use any motor. So, it's a nice driver, but it doesn't make the encoder any cheaper.
- TFortunato 9y ago
  That's a bit of an over simplification, but for a hobbyist application, sure. You are absolutely right that the encoder is a BIG part of your system design, but the motor quality will make a difference. If you are doing something like a robotic arm, or slow speed motor control, you don't just care about encoder ticks, you also start caring about things like torque ripple in the motor if you want decent motion quality, regardless of how good your encoder is!
- _up 9y ago
  You can get cheap Magnetic Encoders. https://www.aliexpress.com/wholesale?catId=0&SearchText=magnetic+encoder https://www.aliexpress.com/wholesale?catId=0&SearchText=magn...
pasta 9y ago
Most industrial motors are also 'cheap', but controlling them is expensive. There are two things that matter: accuracy and repeatability. Most of the time accuracy is not a problem. But repeatability is. For example when you move something heavy a motor can loose a step. When you don't know this the rest of the accurate moves are out of control. That's why industrial controllers have good feedback systems. They know a step was performed. If not, you can act on it. So it's more about control than about motors. But cheap motors wear out faster.
- TFortunato 9y ago
  "Losing a step" makes me think you are thinking about stepper motors, which can be a problem, but for brushless motors it's a bit more complicated than that, since we don't drive them in the same stepwise fashion.
  - pasta 9y ago
    Yes I simplified. But in a way servos are also step/pulse controlled. Edit: as other point out 'controlled' is not the best word here. Maybe 'positioned' would have been better.
    - jacquesm 9y ago
      No, they are not, servos simply do not step, and whatever pulse there is is PWM to control the torque without overheating the driver in an analogue domain. There is no reference based on a 'step' or a 'pulse', there is only the desired position and the actual position and the difference between the two can be quite large, much larger than with a stepper which can by definition be at most one step ahead or behind or it is game over. This gets very interesting once you start to combine servos on multiple axis and you want to limit your maximum error compared to some desired trajectory.
      - pasta 9y ago
        I know servos don't step, but doesn't the decoder 'count' steps? But I totaly agree with you, they are completely different. Maybe in this case it was not very clever to oversimplify the problem. By the way: you point out what I think is great about this business. So much work has been done to control motors very accurate. It's amazing what CNC machines can do today. And also how software optimized motion paths (gcode). And now this hardware. Great stuff!
TaylorAlexander 9y ago
Yes. There are caveats related to long term durability, but you said "for hobbyists" who I think are less concerned with that aspect. As far as up front performance the answer is yes. Others have explained the details so I'm just adding to the "yes" camp. Brushless D.C. Motors are the way to go for robotics in many actuation situations for the near to medium term (next decade at least) and the lack of suitable low cost controllers (this is "low cost") has been a major issue, so this product is excellent. Source: am robotics engineer in Silicon Valley building my own brushless powered robot arm as a hobby and I'm an alpha contributor to the Odrive project. I've also designed my own brushless controllers [1] and built brushless linear motors. [1] https://youtu.be/vbrzxlRpC0k https://youtu.be/vbrzxlRpC0k

Can someone more familiar with embedded design explain a bit more on this? Can this really turn cheap motors into industrial level motors suitable for hobbyists?

TFortunato 9y ago

I'm on a cell phone, so I'll be brief, but can add more detail later. I've been doing motor drivers and embedded work (software and electronics) for robotics for a while, and did work on motor driver ICs before that, so this is kind of my wheelhouse! Briefly: I can tell you that the electronics and software are only a few parts of the overall equation here. Yes, this does look like (from the demo video results), a decent driver design, however quality of the motor DOES matter, and will eventually become a limiting factor if you are lookig for high precision or high power, as you start to run into things like torque digging, motor heating, etc. There are also little things in the driver design that can bite you if you aren't careful, but I'd need to look at the schematics to comment. I'm not trying to crap on the project or designer. There was clearly some thought and care put into this! I just don't want people to expect magic, or to think that the only difference between an industrial servo and a hobbyist motor is the electronics. That said, you can get VERY far with good electronics and control software! A hobbyist project will probably do just fine with something like this (or a motor driver reference design from the chip manufacturers), and by the time they run into limits of those designs and hobbyist motors, they'll probably have a pretty good idea of where they need to go as a next step! I'll take a closer look at this design later, and update if anyone is interested.

gvb 9y ago
Please :-) Here are the documentation links to get you started: Hardware: https://github.com/madcowswe/ODriveHardware/ https://github.com/madcowswe/ODriveHardware/ v3.2 schematic: https://github.com/madcowswe/ODriveHardware/blob/master/v3/v3.2docs/schematic_v3.2.pdf https://github.com/madcowswe/ODriveHardware/blob/master/v3/v... Firmware: https://github.com/madcowswe/ODriveFirmware https://github.com/madcowswe/ODriveFirmware PC config and analysis support: https://github.com/madcowswe/ODrive https://github.com/madcowswe/ODrive FPGA: https://github.com/madcowswe/ODriveFPGA https://github.com/madcowswe/ODriveFPGA "... the FPGA logic and software that runs on the FPGA based ODrive. This is not currently in development, but may be resumed at some later date." ---- The hardware is based on a STM32F405RGT6[1] driving two TI DRV8301 brushless motor controller chips[2] and a bunch of MOSFETs to handle the power switching. I/O is a USB, CAN with driver chip, and SPI unbuffered on headers. [1] High-performance foundation line, ARM Cortex-M4 core with DSP and FPU, 1 Mbyte Flash, 168 MHz CPU, ART Accelerator http://www.st.com/en/microcontrollers/stm32f405rg.html http://www.st.com/en/microcontrollers/stm32f405rg.html [2] DRV8301 Three-Phase Gate Driver With Dual Current Shunt Amplifiers and Buck Regulator http://www.ti.com/lit/ds/symlink/drv8301.pdf http://www.ti.com/lit/ds/symlink/drv8301.pdf
- carterehsmith 9y ago
  Sorry for being off-topic. I just want to say, "STM32F405RGT6" is possibly the most hardcore product/model name ever. Just beautiful.
  - revelation 9y ago
    There are usually a dozen variants of the same microcontroller design just with different peripherals, amount of memory, packaging.. You could just as well say STM32 or STM32F4 and that is pretty much 99.9% of the information you need to know :)
  - makomk 9y ago
    It packs a lot of information in. STM32F4 is ST Micro's range of high-performance ARM Cortex-M4 microcontrollers with FPU, STM32F405 is a particular family of devices in that range differing mainly in package and memory size, R specifies that it's the 64-pin variant, G indicates that it's the version with 1024KB of flash, T is the LQFP package, and 6 is for -40 to 85 °C temperature range. Most of this is shared across the entire STM32 range of devices.

tyingq 9y ago

I suspect there's no free lunch here. If they are designed for hobby r/c aircraft, they are designed for shorter runs with lots of free prop-driven fan cooling. Not for sustained runs without a prop cooling it. So, it would likely work, but have a shorter lifetime. The barrier to using them was having a low voltage / high current controller. This fills that gap. So, not a bad idea, but there's almost surely a durability tradeoff. And maybe that's fine for a hobbyist cnc application.

TaylorAlexander 9y ago
Cooling can be an issue if you drive them near their rated power without adequate cooling. And absolutely they won't have the same quality of construction as true industrial devices. However they are sufficiently powerful to be useful and cost effective at continuous duty levels below their max rated power.
madcowswe 9y ago
One thing to keep in mind is that for many robotics applications, the duty cycle for high torque (i.e. acceleration) is often quite low. So they may still run fairly cool.

analog31 9y ago

Historically, hobbyists have chosen stepping motors because they can be controlled with a fairly simplistic controller, and there are lots of solutions out there... check out some of the step motor drive boards at Pololu Electronics. But stepping motors have limitations, namely speed and torque per unit motor size. Note that as a hobbyist, I'm still living in the stepper motor world, so I'm interested in this project. Brushless servo motors offer the potential for much higher torque and speed in a small package, but require a different form of electronic control, and the gist of this project is that such controls haven't been available for hobbyists. So it's a matter of finding a gap in the existing project / product space, and filling it. Note that e-bikes use brushless servo motors, so somebody has done the math on what motor technology is most efficient. I also think these motors are in electric cars, and even appliances such as washing machines. I will be reading with interest. I'll also start keeping an eye out for what kinds of motors are available. As for "industrial level," I'd say that it's a matter of pushing machine speeds up to a level similar to what you might see in a factory. Often, with stepper motor driven gadgets, you accept the fact that your machine will take a long time to do anything, but who cares, it's a hobby. On the industrial side, you very quickly run into the situation where your motor is no longer the limiting factor affecting speed and precision, but the design and assembly of the mechanism is.

TFortunato 9y ago
Yeah, brushless is definitely the way to go for efficiency, and good smooth motion. Stepper for an e-bike or washing machine (Not a BLDC either, but...) would be nuts, and in general steppers are really for cheap semi-decent control, not for anything where precision is really needed.
- TaylorAlexander 9y ago
  My colleague had a motor from a newer washing machine out on his desk, and it did appear to be a BLDC. Alternating magnets with three phases of coils as you'd expect. Driven from rectified 120V AC!
  - TFortunato 9y ago

bsder 9y ago

Sure, the issue with brushless motors isn't the motor, it's the encoder. The encoder is what "closes the loop" and allows you to get the accuracy you need. If you have a way to relate the position of the thing being controlled to the motor position, then you can use any motor. So, it's a nice driver, but it doesn't make the encoder any cheaper.

TFortunato 9y ago
That's a bit of an over simplification, but for a hobbyist application, sure. You are absolutely right that the encoder is a BIG part of your system design, but the motor quality will make a difference. If you are doing something like a robotic arm, or slow speed motor control, you don't just care about encoder ticks, you also start caring about things like torque ripple in the motor if you want decent motion quality, regardless of how good your encoder is!
_up 9y ago
You can get cheap Magnetic Encoders. https://www.aliexpress.com/wholesale?catId=0&SearchText=magnetic+encoder https://www.aliexpress.com/wholesale?catId=0&SearchText=magn...

pasta 9y ago

Most industrial motors are also 'cheap', but controlling them is expensive. There are two things that matter: accuracy and repeatability. Most of the time accuracy is not a problem. But repeatability is. For example when you move something heavy a motor can loose a step. When you don't know this the rest of the accurate moves are out of control. That's why industrial controllers have good feedback systems. They know a step was performed. If not, you can act on it. So it's more about control than about motors. But cheap motors wear out faster.

TFortunato 9y ago
"Losing a step" makes me think you are thinking about stepper motors, which can be a problem, but for brushless motors it's a bit more complicated than that, since we don't drive them in the same stepwise fashion.
- pasta 9y ago
  Yes I simplified. But in a way servos are also step/pulse controlled. Edit: as other point out 'controlled' is not the best word here. Maybe 'positioned' would have been better.
  - jacquesm 9y ago
    No, they are not, servos simply do not step, and whatever pulse there is is PWM to control the torque without overheating the driver in an analogue domain. There is no reference based on a 'step' or a 'pulse', there is only the desired position and the actual position and the difference between the two can be quite large, much larger than with a stepper which can by definition be at most one step ahead or behind or it is game over. This gets very interesting once you start to combine servos on multiple axis and you want to limit your maximum error compared to some desired trajectory.
    - pasta 9y ago
      I know servos don't step, but doesn't the decoder 'count' steps? But I totaly agree with you, they are completely different. Maybe in this case it was not very clever to oversimplify the problem. By the way: you point out what I think is great about this business. So much work has been done to control motors very accurate. It's amazing what CNC machines can do today. And also how software optimized motion paths (gcode). And now this hardware. Great stuff!

TaylorAlexander 9y ago

Yes. There are caveats related to long term durability, but you said "for hobbyists" who I think are less concerned with that aspect. As far as up front performance the answer is yes. Others have explained the details so I'm just adding to the "yes" camp. Brushless D.C. Motors are the way to go for robotics in many actuation situations for the near to medium term (next decade at least) and the lack of suitable low cost controllers (this is "low cost") has been a major issue, so this product is excellent. Source: am robotics engineer in Silicon Valley building my own brushless powered robot arm as a hobby and I'm an alpha contributor to the Odrive project. I've also designed my own brushless controllers [1] and built brushless linear motors. [1] https://youtu.be/vbrzxlRpC0k https://youtu.be/vbrzxlRpC0k