I am building some actuators (quasi-direct-drive) and thought to share this here. For this I will use the multistar 9235-100kv BLDC motors and VESC 100A as motor controllers. I made some minor modifications on the original design to suit my needs. For example I made i dual-version to work as a hip joint motion as the [font=arial, sans-serif][size=2][highlight=#ffffff]Agility [/highlight][/size][/font][font=arial, sans-serif]Robotics Cassie[/font].
This looks like a very refined design, but can’t quite figure out your application? You’re using two fans, so perhaps a mini ROV? Very curious to know more.
[size=2][font=Arial]They will be used for a [highlight=#ffffff]humanoid robot. More or less like the [/highlight][highlight=#ffffff]Agility [/highlight]Robotics Cassie. Total 10 actuators controlled with 10 VESC´S.[/font][/size]
[font=arial, sans-serif][size=2]Something like this:[/size][/font]
Tonight I did the first test drive of the actuator (Current limit is set to 5A.)
I would not have guessed that. Thanks for sharing!
If each actuator can consume up to 100A, and you’ll be using 10 of them, wouldn’t the theoretical max current be 1KW? If normal operation has them running at 1/4 power, 250A still seems quite high?
Still in early stages of this prototype. Something around 28W/Motor. 10x28=280W. Also very rough calculations since all motors will note operate actively.
But Yes. One would need a couple… of batteries
From their site, it seems each motor can provide 2800W (2.8KW), operating at 8-12S (~30V to ~45V), No load at all is 1A, so yeah, batteries batteries batteries.
last couple of days we have been busy updating / modifying the firmware for the VESC (based on FW3.33).
The orginal firmware does not allow multi-turn position control and has a short way rotation (rotates the fastes way in any direction to set-point)
Key functions
#1 Multi-turn posistion control (controlling motor position over multiple encoder turns, for example 0-2160Degress) #2 Removed shortest route rotation -+180 degress #3 Implement a cascaded style position, velocity and current control loop. The idea was previously tested on our simulator for cascaded position and speed control (http://grauonline.de/alexwww/motorsim/motorsim.html) #4 Handle encoder rollover up or down. #5 default #define AS5047_USE_HW_SPI_PINS 1 (which will use HW SPI instead for encoders)
Here is a simple motion test over ROS:
Hardware:
#9235 -100KV Multistar brushless outrunner #AMS AS5048A (Over SPI) #3D printed gearbox #Maytech 100A Vesc
We will continue to work on improvments in the software side.
@cbenson I saw robotshop are selling a Maytech VESC maybe you guys canto test this firmware? which increases the use in robotics.
Nice! Waiting to hear results of a torque test (vs current draw). Unfortunately other projects at RobotShop are more pressing at the moment. Great to know you’re up to modifying VESC firmware!
here you have some torque numbers
Current limit 10A = 7Nm
Current limit 30A = 14Nm
Current limit 60A = 28Nm
Current limit 100A = * Peak torque (theoretical): 56 Nm with extra air cooling!
Nice work. The current vs. torque values you posted here are measured statically (0 speed, stall torque) or at a certain speed? Did you also test how much friction in the 3D printed gearbox?
I also want to use 3D printed gearboxes for BLDC motors. I found two nice 3D printed gearbox projects: planetary gearbox (OpenTorque) and cycloidal gearbox (https://hackaday.io/project/157812-3d-printed-robot-actuator). I’m not sure which one is better for a walking/running robot. Do you have any suggestions?
By the way, is Nylon better than the alloy 910 for the gears?
I see. I am using the OpenTorque with minor mods. I have no experience of the other one you mention.
I have only printed with alloy 910 which works very well for gears.
