Drive the Polaris Ranger#

This tutorial shows how to start a session with the Polaris and how to drive it with the keyboard. It gives each key, the gear lever, the drive modes, the drive-by-wire key and the content of the HUD.

Before You Start#

You have the packaged game. Refer to Run the Packaged Game.
You did the first drive with the Maxxum. Refer to First Drive.
You have a keyboard and a mouse. The game must have a window on a display.

The Polaris of the game is the vehicle of the Purdue lab: a Polaris Ranger CREW XP 1000 with the Dataspeed drive-by-wire. Polaris Ranger Dynamics gives the model of the vehicle.

Start the game without options.
```
Packaged/Linux/Acres.sh
```
Expected Result

The game shows the menu.
Select New Simulation.
Open the tab Vehicle.
Set Vehicle to Polaris Ranger CREW XP 1000 (DBW).

Note

The selection Both (Maxxum and Polaris, Multi-Agent) starts the two vehicles. Refer to Run Several Vehicles.
Set Polaris Finish to the paint that you want.

Menu Name Option Value

Graphite / Orange graphite

Forest Green / Bronze forest_green

Desert Tan / Charcoal desert_tan

Deep Blue / Silver deep_blue

The option value is for -PolarisFinish= on the command line. The finish changes only the paint of the mesh. The physics stays the same.
Select Start.

Expected Result

The Polaris is in front of the ICSC garage and points to the north. A help box with the title Polaris Ranger shows the main keys for 12 s.

Start a Session from the Command Line#

Start the game with the option -Vehicle=polaris.

Packaged/Linux/Acres.sh -VehicleDemo -Vehicle=polaris -PolarisFinish=forest_green

Expected Result

The log of the game contains these two lines.

ACRES_POLARIS_CONFIG file=../../../Acres/Content/Simulation/polaris.json keys=159 unknown=0
  mass_kg=1233.0 cg_m=(1.243, 0.014, 0.655) inertia_kg_m2=(318, 1374, 1475)
  steering_ratio=11.976 centre_deg=12.53 speed_scale=0.930 finish=forest_green
ACRES_RIG_LAYOUT vehicle=polaris finish=forest_green wheel_centre_max_error_cm=0.000
  wheelbase_m=2.8702 track_m=1.310 physics_mass_kg=1233.0

Each entry is one line in the log. The line breaks are only for this page.

These options apply to the Polaris. Command-Line Options gives all options.

Name	Type	Default	Description
`-Vehicle=`	text	`maxxum`	The vehicle of the session: `maxxum` or `polaris`.
`-PolarisFinish=`	text	`graphite`	The paint: `graphite`, `forest_green`, `desert_tan` or `deep_blue`.
`-PolarisOccupants=`	integer	1	The number of occupants, 0 to 6. It changes the mass.
`-PolarisSet=`	text		Overrides of model parameters: `key=value` pairs with `;` between them.
`-PolarisConfig=`	path	`Simulation/polaris.json`	The parameter file of the vehicle.
`-PolarisSensorConfig=`	path	`Simulation/sensors_polaris.json`	The sensor overlay of the Polaris.
`-CameraCab`	flag	off	Starts the session in the driver view.
`-DbwLog`	flag	off	Writes the drive-by-wire reports to `dbw.csv`.

Keys#

Hold Tab in a session to see all keys.

Key	Function
`W`	Throttle. The pedal goes to 100 % in 0.6 s and back to 0 in 0.25 s.
`S` or `Space`	Brake. The pedal goes to full pressure in 0.35 s and back to 0 in 0.3 s.
`A` and `D`	Steer to the left and to the right. The steering wheel turns at 360 deg/s to the lock at 487°.
`[`	Moves the gear lever one position in the direction of P.
`]`	Moves the gear lever one position in the direction of L.
`V`	Changes between R and L. The speed must be below 0.3 m/s.
`L`	The AWD switch: AWD, then 2WD, then Turf, then AWD again.
`F3`	The enable button and the disable button of the drive-by-wire.
`C`	Changes between the chase view and the driver view.
Mouse	Turns the view. The wheel changes the distance of the chase view.
`R`	Puts the vehicle back at its start position.
`F2`	Goes to the next vehicle of a session with more than one vehicle.
`I`	Shows or hides the cards at the right, which include the drive-by-wire card.
`F1`	Shows or hides the engineering panel.
`1` to `6`, `0`	Surface override: asphalt, concrete, gravel, dry, wet, mud. `0` uses the mapped surface.
`F6`	Starts and stops the sensor recording.
`F12`	Makes a screenshot.
`Esc`	Pauses a session that started from the menu. Stops the game in a session from the command line.

When you release A and D, the steering wheel goes back to the straight position at 540 deg/s. The straight position is a steering wheel angle of 12.5°. This is the fitted centre of the real vehicle.

Gear Lever#

The lever has the positions P, R, N, H and L in this sequence. The session starts in P, so the vehicle stays at its start position on a slope. Hold the brake and push ] four times to select L before you drive.

Position	Use	Top Speed in the Model
P	Park. A pawl locks the transmission.
R	Reverse.
N	Neutral. The engine does not drive the wheels.
H	High range.	26.7 m/s (96 km/h)
L	Low range. The lab uses this gear for its tests.	13.6 m/s (49 km/h)

The transmission accepts a new gear only below 0.3 m/s. The change has a duration of 1 s and goes through neutral. If you move the lever at a higher speed, the gear changes after the vehicle stops.

Drive Modes#

The key L moves the AWD switch.

Mode	Rear Axle	Front Axle	Use
AWD	Locked	Engages when the rear wheels slip more than approximately 7.5 %	Soft or wet ground. This is the default.
2WD	Locked	Not driven	Firm ground.
Turf	Open	Not driven	Tight turns on grass. The inner rear wheel does not scrub.

A locked rear axle makes a turn wider. In the model the path curvature at 180° of steering wheel angle is 12.7 % smaller than in Turf.

Drive-by-Wire Key#

The key F3 is the enable button of the Dataspeed system. A client on the vehicle bridge usually sends this command.

When the system is enabled, the pedals and the steering of the driver are off. The vehicle waits for commands.
A subsystem without commands does nothing. The vehicle then moves without throttle and without brake.
If you press W, S, Space, A or D while the system is enabled, this is an override. The system disables itself.
Press F3 again to enable the system after an override.

CAUTION

Do not press F3 on a slope when no client sends commands. The vehicle has no brake until you press a pedal key.

Drive-by-Wire and ULC gives the commands and the watchdog. First ROS 2 Session shows how to send commands.

Driver View#

The key C changes to the driver view. The eye point is the front left seat, 1.55 m above the ground. The mouse turns the view 150° to each side, 60° down and 40° up. Press C again for the chase view. The option -CameraCab starts the session in the driver view.

What the HUD Shows#

The bottom right corner shows the engine speed, the gear and the speed.

The bar shows the engine speed. The last 8 % of the range are red. The rev limiter is at 8000 rev/min.
The badge shows the engaged gear as a letter: P, R, N, H or L. The badge is red in reverse.
The number shows the speed in km/h.

The card Drive-by-Wire at the right shows the state of the drive-by-wire. The key I shows or hides it.

Row	Content
Badge	`Disabled`, `Enabled · Bridge`, `Enabled · Follower` or `Override`
Steering	The steering wheel angle, the steering reference, and `DBW` or `driver` with the command type
Road Wheel	The bicycle angle, the drive mode (`AWD`, `2WD`, `turf`) and the ratio of the CVT
Throttle	The emulated pedal and the pedal command in percent, and `DBW` or `driver`
Brake	The line pressure and the pressure command in bar, and `DBW` or `driver`
Gear	The engaged gear, the gear command and the lever position
ULC	The speed reference and the acceleration reference, or `off`. The word `hold` shows the stop hold.
Velocity	The wheel speed of the drive-by-wire and the true speed in m/s

The badge Enabled · Follower shows that a session driver has control, for example a replay. The wheel speed is approximately 7 % less than the true speed. The real wheel speed signal has the same error.

When the sensor recording is on, the bottom centre shows the image of the camera with the title Reolink Camera.

A Short Drive#

This procedure drives the Polaris on the apron of the ICSC garage.

Note

An obstacle is approximately 20 m in front of the start position. Turn before you get there.

Start a session with the Polaris.
Read the card Drive-by-Wire.

Expected Result

The badge shows Disabled. The row Gear shows L. The row Road Wheel shows AWD and CVT 3.20.
Hold W for 2 s, then release it.

Expected Result

The engine speed increases above 1600 rev/min and the clutch engages. The vehicle moves forward. The CVT ratio in the card decreases as the speed increases.
Hold A to turn to the left. Release the key to go straight again.
Hold S until the vehicle stops.

Expected Result

The row Brake shows a line pressure that increases to 80 bar.
Press [ one time to select H.

Expected Result

The badge shows N for 1 s and then H.
Hold W to drive in the high range. Then stop the vehicle with S.
Press V to select R. Hold W to go rearward. Then stop the vehicle.

Expected Result

The badge is red and shows R. The speed number does not show a sign.
Press V again to select L.
Press L two times to select Turf. Drive a tight circle with W and D.

Expected Result

The row Road Wheel shows turf.
Stop the vehicle. Press [ until the badge shows P.

Expected Result

The park pawl holds the vehicle. The vehicle does not move when you release the brake.