Data on Low Torque Required in Skid Steering

In the MSc thesis:

Experimental Comparison of Skid Steering

Vs.

Explicit Steering for a Wheeled Mobile Robot

Benjamin Shamah, Skid Steering is able to compete with explicit steering despite requiring more energy for low radius turns.

At high turning radius, e.g. 12 m, total torque for all wheels in the explicit steering is 400 Nm. For skid steering, it is less than 600 Nm. Not much difference really.

Even skid steering is able to perform at zero radius with a total torque of 

1,700 Nm, compared to 800 Nm for the explicit steering. 

Do not be fooled by wrongful conclusions that are just based on calculations below. The conclusions are not based on the actual data calculated.

Refer to the paper:

Differential Steering Control of Four-Wheel

Independent-Drive Electric Vehicles, written by Jie Tian 1,*, Jun Tong 1 and Shi Luo 2, which you can download from:

https://www.researchgate.net/publication/328507745_Differential_Steering_Control_of_Four-Wheel_Independent-Drive_Electric_Vehicles.

SSV is the skid steering vehicle (SSV) which does not have the Ackerman Steering to assist the turning. DSV is termed as Differential Steering assisted by Ackerman Steering.

This article concludes that SSV is not practical because it requires a huge amount of differental torque to steer. However, the yaw rates in the graphs are not practical and in fact extremely dangerous. The highest yaw rate should just be 0.01 radian per second, corresponding to 1.8 degree per second.

At this yaw rate, the differential torque required for the SSV is also virtually zero. Certainly less than 100 Nm. The DSV is much less but it is understandable because of the Ackerman Steering. There should be zero torque. DSV is used to increase yaw rate only.

The amount of torque is actually a function of the forces required for lateral slip to occur. On gravel, it is much less.

In the book downloadable from: https://www.researchgate.net/publication/228616843_Aerodynamics_of_race_cars, by Joseph Katz, the lateral force at the point of sliding, is less than the weight of the car. This data is for sliding analysis, not for steering.

Experiences with tanks and armoured vehicles using skid steering show that the lateral force required to turn is much less than the weight of the vehicle.