[dhanushs]

So.. The Thar ROXX has been introduced into the market with some best in class off-roading features and probably, first time in India features.. Being the Lead for All-Terrain Capability Development for the ROXX and all other Mahindra products, I thought it'd be best to have a detailed thread on Team-BHP about what these features are and how these features work (on a holistic level), atleast in the ROXX, so that fellow members can put these features to good use.

IntelliTurn (Intelligent Turn Assist)



Intelliturn is a feature which lets you manoever tight offroad terrain (turns) with ease. Basically it brakes the inner rear wheel and fecilitates a tighter turning raidus than geometrically possible by the vehicle architecture.

To start off, let me tell you how to activate the feature in the Thar ROXX. Driver montoring and drive away intent is ON for safety so, you will need to start with..

1. Sitting in your seat.
2. Engine ON
3. Doors Closed.
4. Seatbelts ON.
5. E Parking Brake OFF.

Once your intent is to drive.. Set the

6. Transfer Case in 4Low.
7. Gear in D
8. Choose the terrain you want to drive on - (Snow, Mud or Sand)
9. Then press the IntelliTurn Switch on the right side driver switch bank.


Now you will see a green custer symbol light up similar to the switch you pressed. This means feature is ready and it will faciliate a tighter turn whenever you turn your car. The feature will stay ON till 30 seconds after which will go off, and you will have to press the switch again. However, if you enter a turn then the timer is reset and it will go off only if you dont use it for the next 30 seconds. Once you are in the Turn and the feature is 'actively working' it will do so for 15 seconds which is more than enough for you to complete the turn. After which the feature will turn off. The max speed at which this feature works in 15kmph which is more than enough for a tight turn off-road, beyond which it turns off.

How it works:

On a broader perspective, it brakes the inner rear wheel when turning. So when you are taking a right turn, it will lock the right rear wheel and vice versa when you are taking a left turn. There are multiple sensors at play here which I'm not getting into detail. However, basics would be the steering angle sensor which sends input to the control unit, which figures out based on multiple sensors that the vehicle is intending to turn and increases the brake pressure to the inner rear wheel.

To visualize the turning effect, consider the Center of Gravity as the reference point around which yaw moments are generated due to longitudinal and lateral forces generated by the tires. Usually it's the lateral force generated by the front tires because of the steering geometry. In this case, since one of the rear wheels is being braked (the inner), because of the differential, the outer wheel on the rear axle rotates at a higher speed. The higher rotational speed of the rear outer wheels when compared to the inner wheel will induce a yaw moment about the CG in addition to the forces generated by the front axle (steered tires). This will induce a skid steer in the rear axle and the turning radius of the car is reduced than what would have been achieved with just the front axle steering the car.

Now, since it's a skid steer feature, the efficiency of the turn achieved will depend on the surface μ (Mu = Frictional Co-efficient). Ideally lower the μ, better the turn, as the inner locked wheel can slide more easily. Another factor is the μ between the front axle and rear axle too (off the road you always tend to have different μ in all 4 wheels). This is also why the feature is differently calibrated for different terrain modes and you need to choose the correct terrain mode you are driving on for the feature to work efficiently.

Here's a couple of videos illustrating how the feature works.

https://youtube.com/watch?v=IDZcL8g3lR8?feature=share

https://youtube.com/watch?v=7qjCoJQSM8s?feature=share

P.S - I hope our Indian market evolves with respect to using features safely and responsibly so that, the limit of features like these can be extended to make things really fun to drive.

[dhanushs]

Crawl Smart (Smart Crawl Assist)



Now, at least for me I can say, this would be the most useful feature off-road. It completely transforms your car into a Traction Generator . To explain it in a very basic sense, the car accelerates and brakes itself for you in off-road so that the driver can focus all his attention in steering the car through the obstacle. More on it later. Again to start off, let me tell you how to activate the feature in the Thar ROXX. Driver monitoring and drive away intent is ON for safety so, you will need to start with..

1. Sitting in your seat.
2. Engine ON
3. Doors Closed.
4. Seatbelts ON.
5. E Parking Brake OFF.

Once your intent is to drive.. Set the

6. Transfer Case in 4Low.
7. Gear in D
8. Press the CrawlSmart Switch on the right side driver switch bank.


Once done, and you remove your foot from the brake pedal, the car will start accelerating (and braking if required). The driver is given 7 levels of speed control. The default set speed is Level 2 and the driver can use the cruise speed keypad on the steering to set the speeds to higher or lower as per the terrain demands.

This feature can be used for two purposes:

1. Getting through difficult obstacles. The car will decide/generate the optimum traction, acceleration & deceleration for the given obstacle. (Excellent when used in loose sand and rocky obstacles) for you to cover it.
2. Like an off-road cruise control to have a slow but controlled speed. This is ideal when driving through a forest where the idea is to see what's around you. Removes the stress from having to operate too many controls, and lets you enjoy the scenery.

How it works:

The overall operating logic of the CrawlSmart is pretty complicated and I will stick to the basics. Like mentioned in the above post, off-the-road, you always tend to have different μ in all four wheels. The idea of having the best off-road performance sometimes, is to optimise & make use of the μ on each wheel to have the best forward acceleration of the car. In CrawlSmart, the system uses multiple sensors (eg: Wheel Speed, Forward Acceleration, Yaw, axle torque etc..) to figure out and demand torque on each wheel and gives ONLY the exact amount of torque and not more to each wheel. This is done through controlled brake interventions and engine torque modulation effectively redistributing torque between wheels. The beauty of this system is that if the demand torque based on the surface μ is different for all 4 wheels, the system will optimise the engine torque and brake pressure to achieve variable torque to each of the 4 wheels. This will help each of the wheels to make optimum use of the surface μ to generate forward motion of the car. The system will also try to maintain a constant forward motion based on what the terrain demands by increasing/decreasing the engine torque and the brake torque.

While the idea of the system was to democratise off-roading and enable more and more people enjoy the beauty of off-roading, on rare occasions the system even betters where expert drivers fail (eg: sand)

A coupld of video to showcase how the feature works:

https://www.youtube.com/watch?v=_qZbcY5j8E4

https://youtu.be/XQQj_jv0P_k?t=109

P.S - This is a long video with lot of other content too.. Feel free to watch only the relevant part.

[Aditya]

Thread moved out from the Assembly Line. Thanks for sharing!

[dhanushs]

Well, let's also talk about a couple of more other features which may not be as unique as the features discussed above, but are not found in all 4x4's.

The E-Locking Differential & the Terrain Modes.

Electronic Locking Differential



So, the Thar ROXX is the first Mahindra to be equipped with the Electronic Locking Differential(ELD). The older Thar came with the Mechanical Locking Diffs (MLD). Similar to the old MLD, the ELD too is a mechanical device inside the rear diffs, which locks the left and right axle shaft at a same speed to prevent wheel slip and to have 100% of available torque to any wheel. The difference here would be that ELD is driver controlled, unlike automatic MLD, and can be switched ON or OFF as required. Better control = Better Off-Road Performance.

How to Switch it ON?

You have to be in 4High or 4Low. Thats it. No detailed steps like the other features. . The operating logic would be that, when you press the switch, you have to be below 30kmph + not having any wheel speed difference (~25rpm), for ELD to turn on, and it will remain ON till 40kmph, beyond which it will turn off, but remain passive and will reengage once you drop down to 30kmph.

Now, the ELD and Intelliturn are counterintuitive. So, when you press Intelliturn ON, ELD goes off and you cant turn ELD ON, if IntelliTurn is ON.

Here's a table with operating logic. It's pretty straight forward.



How it works:

Well, the ELD is a mechanical device in the rear differential of the car. There is an Electromagnet which when energised pushes a dog clutch towards engagement. So, when the ELD is off, the torque transfer path from the hypoid gears will ensure it goes through the bevel gears to ensure differential action. When the ELD is switched on, the Dog Clutch engages and changes the torque transfer path bypassing the bevel gears and differential action. This makes sure both the LH and RH axle shafts rotates at the same speed, when ELD is enagaged. The actuation of the clutch is through a switch which the driver can control.

Ideally, ELD has to be used when the driver forsees there will be a wheel slip (Split Mu) and when enagaged, will ensure the car will keep moving without a lack of momentum because of the slip.

Terrain Modes:



Now, the terrain modes are a pretty common feature and I'm not getting into details. However, the idea of terrain modes is that each terrain needs different driver inputs to acc pedals, gear shift, steering etc.. So, the Terrain Modes optimse each system to help the driver optimise his driving to match what the terrain needs.

In each of the modes (Snow, Mud & Sand) terrain modes change the caliberation/settings of the
1. Steering Maps
2. Transmission Shift Points
3. Engine Torque Delivery Curves
4. Traction Control
5. Vehicle Dynamics Control
6. E Locking Differential (to generate max traction)

This ensures the driver is getting the max out of his car in each terrain.

[GhostRider28]

Nice post. Candidly explained. Thanks for sharing. Can the crawl smart also be used for a controlled descent? Or one has to use the descent control?

[brraj]

To make the ROXX still more capable can we add LSD to the front wheels like you had done to your blue project jeep ? or is there any drawback.

[dhanushs]

Originally Posted by GhostRider28

Nice post. Candidly explained. Thanks for sharing. Can the crawl smart also be used for a controlled descent? Or one has to use the descent control?

Yes, like mentioned above. So, in the ROXX the HDC is more focused for on-road use. CrawlSmart will work better downhill.

Originally Posted by dhanushs

...
... To explain it in a very basic sense, the car accelerates and brakes itself for you in off-road so that the driver can focus all his attention in steering the car through the obstacle. ...

Originally Posted by brraj

To make the ROXX still more capable can we add LSD to the front wheels like you had done to your blue project jeep ? or is there any drawback.

Not required here.. Just enable CrawlSmart and drive. It will give you a similar capability like the LSD.

On that topic, putting a front locker/lsd on cars which are not designed for that isnt really advisable. On max demand torque things will break.

[Amrit@wheels]

On a different note, I come from a farmer family and we naturally have a tractor in our village farm house. When I was learning how to drive it (don't ask me why), one of the first thing I was taught was this "IntelliTurn" or using the brake to turn. I always appreciated the usefulness of the technique but I never thought I'd see it become a 'feature' in a car lol...

[Aakash118]

Thanks for the lovely post. From whatever off roading videos I’ve watched on youtube, I always believed the Gurkha to be the most capable off roader in it’s segment. Never knew that Roxx has overtaken it in this regard.

[Turbanator]

Originally Posted by Amrit@wheels

one of the first thing I was taught was this "IntelliTurn" or using the brake to turn. I

You forgot to mention, most tractors have two separate brake pedals, one for the left rear wheel and one for the right rear wheel.

[Amrit@wheels]

Originally Posted by Turbanator

You forgot to mention, most tractors have two separate brake pedals, one for the left rear wheel and one for the right rear wheel.

Sorry, my bad. I thought this was common knowledge. Still, an interesting thing in my opinion.

[Carcrazy60]

Thanks for the great post. I have saved it.

[DirtyDan]

Clever, clever engineering. And, what is just as impressive, a very clear-headed explanation of how/why these features work. Impressive, Dhanushs.

[GhostRider28]

Originally Posted by dhanushs

Yes, like mentioned above. So, in the ROXX the HDC is more focused for on-road use. CrawlSmart will work better downhill..

Interesting indeed. I had the notion that Hill descent control is for offroad use. Does HDC use engine braking and what is the maximum speed limit?

[dhanushs]

Originally Posted by GhostRider28

Interesting indeed. I had the notion that Hill descent control is for offroad use. Does HDC use engine braking and what is the maximum speed limit?

In the ROXX, the HDC is from 9kmph to 35kmph. Off-Road you need speeds much lower than 9kmph, hence. On-Road (for short durations) however is great.

HDC works by controling the brake pressures in all 4 wheels to give you that controlled speed.

Originally Posted by DirtyDan

Clever, clever engineering. And, what is just as impressive, a very clear-headed explanation of how/why these features work. Impressive, Dhanushs.

Thanks Dan