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## Steering and Pivot Tables

Hi,

I've been looking into the M1A2 model, specifically the dynamic component parameters.
Under the steering logic heading, a steering table and pivot table are listed. A steering table is provided, but a pivot table is not.

I tried searching the documentation, but I can't find any mention of the tables. Can you please explain what they are, and how they are used? I'd like to create my own pivot table: what format do I need to use, what do the numbers represent and what effect do they have on the vehicle?

Regards,

Kyle

Best Answer

Hello Kyle,

In vehicle system, the differential component is made up from two vortex basic constraints: a VxDifferential and a VxGearRatio.
The first one is used to model the so call open differential. The second one is used in conjunction with the differential to model partially or fully locks of the differential gears. This allows to model a broad range of different behaviors.

Steering mode

In this mode of steering, the differential is locked with a given lock ratio. This imposes the left and the right track to rotate at a desired speed difference which imposes the vehicle to deviate. The higher the ratio, the higher the speed difference will be and then, the smaller the turning radius.

The user provided "Steering Table CSV File", represents a function of the form y = f(x). In x, there is the steering input values that range between [0.0, 1.0]. In y, values represent a lock ratio. A value of y=1.0 will result in having both tracks rotating at the same speed therefore the vehicle will go straight (so the first entry of tha table should be (0,1). A value of y=2.0, for instance, means that the left side will rotate twice as fast as the right side, therefore, in this case, the vehicle will steer right. The actual turning radius depends on the geometry of the vehicle (mainly its length over width ratio), the linear speed of the vehicle and the property of the material of the ground.

Pivot mode:

In this mode, differential is locked with a lock ratio of 1.0. This imposes the two tracks to rotate in opposite direction. As a result, the vehicle rotate on spot. In addition, the input gear ratio of the differential is used to control the actual speed of the tracks, allowing to control the speed of the pivot.

The user provided "Pivot Table CSV File", represents a function of the form y = f(x). In x, there is the steering input value that range between [0.0, 1.0]. In y, the corresponding value represent the input gear ratio . A value of 0.0 will result in having no speed to be transmitted to the tracks. A value of 2.0, for instance, means that the tracks rotational speed will be twice the speed of the input shaft of the differential. The actual speed of rotation of the vehicle depends on the geometry of the vehicle (mainly its width), and the property of the material of the ground.

Note that, the input shaft of the differential correspond to the output shaft of the transmission. In general, this operation is done on the first gear where the maximum torque is available.

Note that only the positive x domain has to be given in the csv files.

Regards,

Stéphane Lemay

Vortex StudioSupport | Support Vortex Studio

CM Labs Simulations

Office: +1 514 287 1166 | www.cm-labs.com

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Answer

Hello Kyle,

In vehicle system, the differential component is made up from two vortex basic constraints: a VxDifferential and a VxGearRatio.
The first one is used to model the so call open differential. The second one is used in conjunction with the differential to model partially or fully locks of the differential gears. This allows to model a broad range of different behaviors.

Steering mode

In this mode of steering, the differential is locked with a given lock ratio. This imposes the left and the right track to rotate at a desired speed difference which imposes the vehicle to deviate. The higher the ratio, the higher the speed difference will be and then, the smaller the turning radius.

The user provided "Steering Table CSV File", represents a function of the form y = f(x). In x, there is the steering input values that range between [0.0, 1.0]. In y, values represent a lock ratio. A value of y=1.0 will result in having both tracks rotating at the same speed therefore the vehicle will go straight (so the first entry of tha table should be (0,1). A value of y=2.0, for instance, means that the left side will rotate twice as fast as the right side, therefore, in this case, the vehicle will steer right. The actual turning radius depends on the geometry of the vehicle (mainly its length over width ratio), the linear speed of the vehicle and the property of the material of the ground.

Pivot mode:

In this mode, differential is locked with a lock ratio of 1.0. This imposes the two tracks to rotate in opposite direction. As a result, the vehicle rotate on spot. In addition, the input gear ratio of the differential is used to control the actual speed of the tracks, allowing to control the speed of the pivot.

The user provided "Pivot Table CSV File", represents a function of the form y = f(x). In x, there is the steering input value that range between [0.0, 1.0]. In y, the corresponding value represent the input gear ratio . A value of 0.0 will result in having no speed to be transmitted to the tracks. A value of 2.0, for instance, means that the tracks rotational speed will be twice the speed of the input shaft of the differential. The actual speed of rotation of the vehicle depends on the geometry of the vehicle (mainly its width), and the property of the material of the ground.

Note that, the input shaft of the differential correspond to the output shaft of the transmission. In general, this operation is done on the first gear where the maximum torque is available.

Note that only the positive x domain has to be given in the csv files.

Regards,

Stéphane Lemay

Vortex StudioSupport | Support Vortex Studio

CM Labs Simulations

Office: +1 514 287 1166 | www.cm-labs.com

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