Alternate Isaac Kaya Base Driver

This is an alternative to the default Kaya driver from the Isaac SDK.

The kinematics are calculated following the method discussed in Mobile Robot Kinematics: Chapter 3 for a 3-wheel holonomic drive.

General Usage

Setup

In WORKSPACE, change the path to your local Isaac SDK.

For example, I have mine set to this:

local_repository(
    name = "com_nvidia_isaac",
    path = "/bluecamel/isaac",
)

Move app configuration files

To use this package, you can put your app configuration files in the packages/kaya/apps directory.

Everything under this directory operates in the same way as the apps/kaya directory in the SDK, but it can't reference configuration files in the SDK apps directory. It can, however, reference configuration files in the SDK packages directory.

There probably is a better way to do this, but it's easy enough for now.

Deploy

Deploying is similar to deploying from the SDK. Instead of running ./engine/build/deploy.sh, run ./deploy.sh.

For example, deploy the joystick app:

./deploy.sh --remote_user bluecamel -p //packages/kaya/apps:joystick_debug-pkg -d jetpack42 -h 0.0.0.0

Replace bluecamel with your username on the Kaya. Replace 0.0.0.0 with the Kaya's IP address.

BaseDriver component API

isaac.kaya.BaseDriver is compatible with isaac.KayaBaseDriver, but doesn't currently respect all parameters.

Incoming messages

• command [HolonomicBaseControls: StateProto]: The holonomic command to be sent to the motors.
  • speed_x [double]: Linear velocity of the robot in the global reference frame's x axis.
  • speed_y [double]: Linear velocity of the robot in the global reference frame's y axis.
  • angular_speed [double]: Angular speed of the robot in the global reference frame.

Outgoing messages

• state [HolonomicBaseDynamics: StateProto]: The state of the holonomic base.
  • speed_x [double]: Linear velocity of the robot in the global reference frame's x axis. This is calculated from the wheel velocities reported by the Dynamixel motors.
  • speed_y [double]: Linear velocity of the robot in the global reference frame's y axis. This is calculated from the wheel velocities reported by the Dynamixel motors.
  • angular_speed [double]: Angular speed of the robot in the global reference frame. This is calculated from the wheel velocities reported by the Dynamixel motors.
  • acceleration_x [double]: Linear acceleration of the robot in the global reference frame's x axis. This is calculated from the current and previous velocities, as reported by the Dynamixel motors.
  • acceleration_y [double]: Linear acceleration of the robot in the global reference frame's y axis. This is calculated from the current and previous velocities, as reported by the Dynamixel motors.

Sight Channels

These channels are reported to sight if the report_to_sight parameter is set to true.

command

Clamped input speeds and calculated servo speeds as well as the original command message.

message [HolonomicBaseControls: StateProto]

The holonomic command to be sent to the motors.

• command.message.angular_speed [double]: Angular speed of the robot in the global reference frame.
• command.message.speed_x [double]: Linear velocity of the robot in the global reference frame's x axis.
• command.message.speed_y [double]: Linear velocity of the robot in the global reference frame's y axis.

safe_speed

The speeds, clamped according to max_safe_speed and max_angular_speed parameters.

• command.safe_speed.angle [double]: Angular speed of the robot in the global reference frame.
• command.safe_speed.x [double]: Linear velocity of the robot in the global reference frame's x axis.
• command.safe_speed.y [double]: Linear velocity of the robot in the global reference frame's y axis.

servo

The calculated speeds to be commanded to the servos.

• command.servo_back_rad_per_sec [double]: Speed to set the back servo to (in rad/sec).
• command.servo_front_left_rad_per_sec [double]: Speed to set the front left servo to (in rad/sec).
• command.servo_front_right_rad_per_sec [double]: Speed to set the front right servo to (in rad/sec).

current

State reported by the servos.

servo speeds

The current speeds reported by the servos.

• current.motor_back_rad_per_sec [double]: Current speed reported by the back servo.
• current.motor_front_left_rad_per_sec [double]: Current speed reported by the front left servo.
• current.motor_front_right_rad_per_sec [double]: Current speed reported by the front right servo.

ticks

Realtime ticks reported by the servos.

• current.servo_back_ticks [double]: Current realtime ticks reported by the back servo.
• current.servo_front_left_ticks [double]: Current realtime ticks reported by the front left servo.
• current.servo_front_right_ticks [double]: Current realtime ticks reported by the front right servo.

NOTE: The following parameters are currently ignored: debug_speed, debug_servos.

Parameters

• baudrate [int] [default=1000000]: Baud rate of the Dynamixel bus. This is the rate of information transfer.
• debug_mode [bool] [default=false]: If true, the dynamixel driver will be very chatty will print out details about every command that is being run. This currently doesn't behave in the same way as isaac.KayaBaseDriver.
• dynamixel_protocol_version [float] [default=1.0]: The protocol version to use when communicatin with the Dynamixel motors (e.g. 1.0 or 2.0).
• max_angular_speed [double] [default=0.3]: Max turning rate.
• max_safe_speed [double] [default=0.3]: Max safe speed.
• orthogonal_rotation_angle [double] [default=0]: The angle of rotation between the robot frame and global frame.
• report_to_sight [bool] [default=false]: Report messages and servo info to sight.
• servo_back [int] [default=2]: Unique identifier for Dynamixel servo at back. Each motor needs to be assigned a unique ID using the software provided by Dynamixel.
• servo_front_left [int] [default=1]: Unique identifier for Dynamixel servo at front left. Each motor needs to be assigned a unique ID using the software provided by Dynamixel.
• servo_front_right [int] [default=3]: Unique identifier for Dynamixel servo at front right. Each motor needs to be assigned a unique ID using the software provided by Dynamixel.
• torque_limit [double] [default=0.5]: Servo maximum torque limit. Caps the amount of torque the servo will apply. 0.0 is no torque, 1.0 is max available torque.
• wheel_base_length [double] [default=0.125]: Distance of the wheel from robot center of mass. This value is used in kinematic computations.
• wheel_1_angle [double] [default=$\pi$/3]: Angle in the robot reference frame to the first wheel.
• wheel_2_angle [double] [default=$\pi$]: Angle in the robot reference frame to the second wheel.
• wheel_3_angle [double] [default=-$\pi$/3]: Angle in the robot reference frame to the third wheel.
• wheel_radius [double] [default=0.04]: Wheel radius. This value is used in kinematic computations.
• usb_port [string] [default="/dev/ttyUSB0"]: USB port where Dynamixel controller is located at. usb_port varies depending on the controller device (e.g., /dev/ttyACM0 or /dev/ttyUSB0).