ODrive/docs/getting-started.md

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Getting Started

Table of contents

• Hardware Requirements
• Wiring up the ODrive
• Downloading and Installing Tools
• Firmware
• Start odrivetool
• Configure M0
• Position control of M0
• What's next?

Hardware Requirements

You will need:

• One or two brushless motors. It is fine, even recommended, to start testing with just a single motor and encoder.

• One or two quadrature incremental encoder(s)

• A power resistor. A good starting point would be the 50W resistor included with your ODrive.

  Do I really need a power resistor? What values to choose?

  If you don't have a brake resistor, the ODrive will pump excess power back into the power supply during deceleration to achieve the desired deceleration torque. If your power supply doesn't eat that power (which it won't if it's not a battery), the bus voltage will inevitebly rise. If you're unlucky this will break the power supply. At some point, the ODrive's overvoltage protection will trip, after which both motors will be allowed to spin freely. Depending on your machine, this may or may not be a problem.

  The power resistor values you need depends on your motor setup, and peak/average deceleration power.

  To be on the safe side, think about what speed and current limits you want to set for the motor.

  When braking at max speed and with maximum motor current, the power that is dissipated in the power resistor can be calulated as: P_brake = V_emf * I_motor where V_emf = motor_rpm / motor_kv.

• A power supply (12V-24V for the 24V board variant, 12V-48V for the 48V board variant). A battery is also fine.

  What voltage variant do I have?

  On all ODrives shipped July 2018 or after have a silkscreen label clearly indicating the voltage variant.

  ODrives before this may or may not have this label. If you don't have a label, then you can look at the bus capacitors (8 gray cylinder components on the underside of the board). If they read 470uF, you have a 24V version; if they read 120uF you have a 48V version.

Wiring up the ODrive

Make sure you have a good mechanical connection between the encoder and the motor, slip can cause disastrous oscillations or runaway.

All non-power I/O is 3.3V output and 5V tolerant on input, on ODrive v3.3 and newer.

Wiring up the motors

• Connect the motor phases into the 3-phase screw terminals. It is not recommended to use a clip-on connector such as an alligator clip, as this can cause issues with the phase resistance/inductance measurements.
• Connect the power source to the DC terminals. Make sure to pay attention to the polarity.
• Do not apply power just yet.

Wiring up the encoders

Connect the encoder(s) to J4. The A,B phases are required, and the Z (index pulse) is optional. The A,B and Z lines have 3.3k pull up resistors, for use with open-drain encoder outputs. For single ended push-pull signals with weak drive current (<4mA), you may want to desolder the pull-ups.

Downloading and Installing Tools

Most instructions in this guide refer to a utility called odrivetool, so you should install that first.

Windows

1. Install Python 3. We recommend the Anaconda distribution because it packs a lot of useful scientific tools, however you can also install the standalone python.

• Anaconda: Download the installer from here. Execute the downloaded file and follow the instructions.
• Standalone Python: Download the installer from here. Execute the downloaded file and follow the instructions.
• If you have Python 2 installed alongside Python 3, replace pip by C:\Users\YOUR_USERNAME\AppData\Local\Programs\Python\Python36-32\Scripts\pip. If you have trouble with this step then refer to this walkthrough.

2. Launch the command prompt.

• Anaconda: In the start menu, type Anaconda Prompt Enter
• Standalone Python: In the start menu, type cmd Enter

3. Install the ODrive tools by typing pip install odrive Enter
4. Plug in a USB cable into the microUSB connector on ODrive, and connect it to your PC.
5. Use the Zadig utility to set ODrive driver to libusb-win32.

• Check 'List All Devices' from the options menu, and select 'ODrive 3.x Native Interface (Interface 2)'. With that selected in the device list choose 'libusb-win32' from the target driver list and then press the large 'install driver' button.

OSX

We are going to run the following commands for installation in Terminal.

1. If you don't already have it, install homebrew:

/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

2. Install python:

brew install python

3. If you get the error: Error: python 2.7.14_2 is already installed, then upgrade to Python 3 by running:

brew upgrade python

4. The odrive tools uses libusb to communicate to the ODrive:

brew install libusb

5. Now that you have Python 3 and all the package managers, run:

pip3 install odrive

Troubleshooting

1. Permission Errors: Just run the previous command in sudo

sudo pip3 install odrive

2. Dependency Errors: If the installer doesn't complete and you get a dependency error (Ex. "No module..." or "module_name not found")

sudo pip3 install module_name

Try step 5 again

Linux

1. Install Python 3.
2. Install the ODrive tools by opening a terminal and typing pip install odrive Enter
3. Set up USB permissions

    echo 'SUBSYSTEM=="usb", ATTR{idVendor}=="1209", ATTR{idProduct}=="0d[0-9][0-9]", MODE="0666"' | sudo tee /etc/udev/rules.d/91-odrive.rules
    sudo udevadm control --reload-rules
    sudo udevadm trigger

Firmware

ODrive v3.5 and later
Your board should come preflashed with firmware. If you run into problems, follow the instructions here on the DFU procedure before you continue.

ODrive v3.4 and earlier
Your board does not come preflashed with any firmware. Follow the instructions here on the STP Link procedure before you continue.

Start odrivetool

To launch the main interactive ODrive tool, type odrivetool Enter. Connect your ODrive and wait for the tool to find it. Now you can, for instance type odrv0.vbus_voltage Enter to inpect the boards main supply voltage. It should look something like this:

ODrive control utility v0.4.0
Please connect your ODrive.
Type help() for help.

Connected to ODrive 306A396A3235 as odrv0
In [1]: odrv0.vbus_voltage
Out[1]: 11.97055721282959

The tool you're looking at is a fully capable Python command prompt, so you can type any valid python code.

You can read more about odrivetool here.

Configure M0

Read this section carefully, else you risk breaking something.

There is a [separate guide](hoverboard.md) specifically for hoverboard motors.

1. Set the limits:

Wait, how do I set these?

In the previous step we started `odrivetool`. In there, you can assign variables directly by name.

For instance, to set the current limit of M0 to 10A you would type: odrv0.axis0.motor.config.current_lim = 10 Enter

Current limit
odrv0.axis0.motor.config.current_lim [A].
The default current limit, for safety reasons, is set to 10A. This is quite weak, but good for making sure the drive is stable. Once you have tuned the oDrive, you can increase this to 75A to increase performance. Note that above 75A, you must change the current amplifier gains. You do this by requesting a different current range. i.e. for 90A on M0: odrv0.axis0.motor.config.requested_current_range = 90 [A], then save the configuration and reboot as the gains are written out to the DRV (MOSFET driver) only during startup.

Note: The motor current and the current drawn from the power supply is not the same in general. You should not look at the power supply current to see what is going on with the motor current.

Ok, so tell me how it actually works then...

The current in the motor is only connected to the current in the power supply _sometimes_ and other times it just cycles out of one phase and back in the other. This is what the modulation magnitude is (sometimes people call this duty cycle, but that's a bit confusing because we use SVM not straight PWM). When the modulation magnitude is 0, the average voltage seen across the motor phases is 0, and the motor current is never connected to the power supply. When the magnitude is 100%, it is always connected, and at 50% it's connected half the time, and cycled in just the motor half the time.

The largest effect on modulation magnitude is speed. There are other smaller factors, but in general: if the motor is still it's not unreasonable to have 50A in the motor from 5A on the power supply. When the motor is spinning close to top speed, the power supply current and the motor current will be somewhat close to each other.

Velocity limit
odrv0.axis0.controller.config.vel_limit [counts/s].
The motor will be limited to this speed. Again the default value is quite slow. Calibration current
You can change odrv0.axis0.motor.config.calibration_current [A] to the largest value you feel comfortable leaving running through the motor continuously when the motor is stationary. If you are using a small motor (i.e. 15A current rated) you may need to reduce calibration_current to a value smaller than the default.

2. Set other hardware parameters

odrv0.config.brake_resistance [Ohm]
This is the resistance of the brake resistor. If you are not using it, you may set it to 0. Note that there may be some extra resistance in your wiring and in the screw terminals, so if you are getting issues while braking you may want to increase this parameter by around 0.05 ohm.

odrv0.axis0.motor.config.pole_pairs
This is the number of magnet poles in the rotor, divided by two. To find this, you can simply count the number of permanent magnets in the rotor, if you can see them. Note: this is not the same as the number of coils in the stator. If you can't see them, try sliding a magnet around the rotor, and counting how many times it stops. This will be the number of pole pairs. If you use a magnetic piece of metal instead of a magnet, you will get the number of magnet poles. odrv0.axis0.motor.config.motor_type
This is the type of motor being used. Currently two types of motors are supported: High-current motors (MOTOR_TYPE_HIGH_CURRENT) and gimbal motors (MOTOR_TYPE_GIMBAL).

Which motor_type to choose?

If you're using a regular hobby brushless motor like this one, you should set motor_mode to MOTOR_TYPE_HIGH_CURRENT. For low-current gimbal motors like this one, you should choose MOTOR_TYPE_GIMBAL. Do not use MOTOR_TYPE_GIMBAL on a motor that is not a gimbal motor, as it may overheat the motor or the ODrive.

Further detail: If 100's of mA of current noise is "small" for you, you can choose MOTOR_TYPE_HIGH_CURRENT. If 100's of mA of current noise is "large" for you, and you do not intend to spin the motor very fast (Ω * L << R), and the motor is fairly large resistance (1 ohm or larger), you can chose MOTOR_TYPE_GIMBAL. If 100's of mA current noise is "large" for you, and you intend to spin the motor fast, then you need to replace the shunt resistors on the ODrive.

Note: When using gimbal motors, current_lim and calibration_current actually mean "voltage limit" and "calibration voltage", since we don't use current feedback. This means that if you set it to 10, it means 10V, despite the name of the parameter.

If using encoder
odrv0.axis0.encoder.config.cpr: Encoder Count Per Revolution [CPR]
This is 4x the Pulse Per Revolution (PPR) value. Usually this is indicated in the datasheet of your encoder. If not using encoder

• If you wish to run in sensorless mode, please see Setting up sensorless.
• If you are using hall sensor feedback, please see the hoverboard motor example.

3. Save configuration

You can save all .config parameters to persistent memory so the ODrive remembers them between power cycles.

• odrv0.save_configuration() Enter.

Due to a known issue it is strongly recommended that you reboot following every save of your configuration using odrv0.reboot().

Position control of M0

Let's get motor 0 up and running. The procedure for motor 1 is exactly the same, so feel free to substitute axis0 wherever it says axis0.

1. Type odrv0.axis0.requested_state = AXIS_STATE_FULL_CALIBRATION_SEQUENCE Enter. After about 2 seconds should hear a beep. Then the motor will turn slowly in one direction for a few seconds, then back in the other direction.

What's the point of this?

This procedure first measures your motor's electrical properties (namely phase resistance and phase inductance) and then the offset between the motor's electrical phase and the encoder position.

The startup procedure is demonstrated here.

Note: the rotor must be allowed to rotate without any biased load during startup. That means mass and weak friction loads are fine, but gravity or spring loads are not okay. Also note that in the video, the motors spin after initialization, but in the current software the default behaviour is not like that.

Help, something isn't working!

Check the encoder wiring and that the encoder is firmly connected to the motor. Check the value of hex(odrv0.axis0.error) and then refer to the error code documentation for details.

Once you understand the error and have fixed its cause, you may clear the error state with (odrv0.axis0.error = 0 Enter) and retry. You may also need to clear the error state of other subcomponents (e.g. odrv0.axis0.motor.error = 0).

2. Type odrv0.axis0.requested_state = AXIS_STATE_CLOSED_LOOP_CONTROL Enter. From now on the ODrive will try to hold the motor's position. If you try to turn it by hand, it will fight you gently. That is unless you bump up odrv0.axis0.motor.config.current_lim, in which case it will fight you more fiercely.
3. Send the motor a new position setpoint. odrv0.axis0.controller.pos_setpoint = 10000 Enter. The units are in encoder counts.

Other control modes

The ODrive also supports velocity control and current (torque) control. Velocity control
Set odrv0.axis0.controller.config.control_mode = CTRL_MODE_VELOCITY_CONTROL.
You can now control the velocity with odrv0.axis0.controller.vel_setpoint = 5000 [count/s]. Current control
Set odrv0.axis0.controller.config.control_mode = CTRL_MODE_CURRENT_CONTROL.
You can now control the current with odrv0.axis0.controller.current_setpoint = 3 [A].

Note: There is no velocity limiting in current control mode. Make sure that you don't overrev the motor, or exceed the max speed for your encoder.

What's next?

You can now:

• See what other commands and parameters are available, including setting tuning parameters for better performance.
• Control the ODrive from your own program or hook it up to an existing system through one of it's interfaces.
• See how you can improve the behavior during the startup procedure, like bypassing encoder calibration.

If you have any issues or any questions please get in touch. The ODrive Community warmly welcomes you.