ODrive/docs/quick-start.md

Quick Start Guide

Table of contents

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

Wiring up the ODrive

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

All non-power I/O is 3.3V output and 5V tolerant on input, except:

__ODrive v3.2__: GPIO 3 and GPIO 4 are __not__ 5V tolerant.

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 a 0.47 ohm, 50W resistor

  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_kv * V_bus.

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

1. Wire up the motor phases into the 3-phase screw terminals, and the power resistor to the AUX terminal. Wire up the power source to the DC terminal, make sure to pay attention to the polarity. Do not apply power just yet.

2. Wire up 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.

• If 'Odrive version 3.x' is not in the list of devices upon opening Zadig, check 'List All Devices' from the options menu. With the Odrive selected in the device list choose 'libusb-win32' from the target driver list and select the large 'install driver' button.

Linux/macOS

1. Install Python 3.
2. Install the ODrive tools by opening a terminal and typing pip install odrive Enter
3. Linux: 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/50-odrive.rules
    sudo udevadm control --reload-rules
    sudo udevadm trigger # until you reboot you may need to do this everytime you reset the ODrive

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.

Configure M0

Read this section carefully, else you risk breaking something.

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

   • The current limit: odrv0.axis0.motor.config.current_lim [A]. The default current limit, for safety reasons, is set to 10A. This is quite weak, and good for making sure the drive is stable. Once you have tuned the drive, you can increase this to 75A to get some performance. Note that above 75A, you must change the current amplifier gains.
     • 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.
   • The velocity limit: odrv0.axis0.motor.config.vel_limit [counts/s]. The motor will be limited to this speed; again the default value is quite slow.
   • You can change odrv0.axis0.motor.config.calibration_current [A] to the largest value you feel comfortable leaving running through the motor continously when the motor is stationary.

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.

   • odrv0.axis0.motor.config.pole_pairs: This is the number of magnet poles in the rotor, divided by two. 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.

   • 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 (omega * 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.

   • 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.

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 replace read "axis1" 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 initalisation, but in the current software the default behaviour is to do position control to position 0 (i.e. the position at startup)

   My motor doesn't beep or doesn't turn

   Make sure the motor wires are connected firmly. Check the value of odrv0.axis0.error and then refer to the error code documentation for details.

   Once you have understood the error and fixed its cause, you may clear the error state (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).

2. Type odrv0.axis0.motor.config.pre_calibrated = True Enter and then odrv0.save_configuration() Enter. This will save all the configuration and calibration you just did so the next time you start the device it's already ready to go. Except for one thing: you need to run the encoder offset calibration after every power cycle.

3. Type odrv0.axis0.requested_state = AXIS_STATE_CLOSED_CONTROL_LOOP 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.

What's next?

You can now:

• Set the 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

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