Knowledge Base

Article Number: 42 | VC3 | VC4 | Post Date: October 6, 2017 | Last Updated: October 6, 2017

I’m having trouble understanding what the difference is between a sequence’s “time” and “steering time”. Which one is the time where a steering input starts?

Driver inputs to the simulation model are explained in Chapter 8 of the User’s Guide. Steering controls are also reviewed in various other posts, such as

Below we will provide some additional insights to the steering input feature. 

Suppose we want our vehicle to operate under the following sequence of events:
1.    Go straight for 1 second
2.    Over a 5 second interval, gradually steer left with a maximum 30 degree steering angle (at the front wheels). 
3.    Hold the 30 degree steering angle for 2 seconds
4.    Over a 2 second interval, gradually steer right with a maximum -20 degree steering angle (at the front wheels).
5.    Hold the -20 degree steering angle for 2 seconds

We can accomplish this in Virtual CRASH by simply adding sequences into the sequence menu. This will automatically occur if you use the fast control icons; otherwise, you can left-click on your vehicle, go to the sequences menu in the left-side control panel, and press “add sequence”. Touching a fast control icon or pressing “add sequence” will automatically cause an initial sequence entry to appear in the sequences menu corresponding to the vehicle’s initial driver input at time = 0 seconds. Pressing “add sequence” two more times will place two additional sequence entries into the sequences menu. Note, with no sequences yet defined in the sequences menu, if you use the interpositions boxes to select a time greater than time = 0 s in the simulation, and then touch a fast control icon, two sequences entries will automatically be placed into the sequences menu, the first corresponding to the initial 0 deg steering no braking entry at time = 0 seconds, and the second corresponding to your entry using the fast control icon, whose time depends on which interposition you selected. 

With our three sequences added to our sequences menu, we can define each entry according to our desired sequence of events listed above. The first sequence entry is as follows:

The second is:

The third sequence is given by:

Note, the “time” parameter is the time the entry is to start with respect to the prior sequence entry. The first sequence entry always begins at time = 0 seconds. The “steering time” is the duration over which the steering angle is to go from the prior entry’s steering angle to the current entry’s steering angle. 

The sequences will progress as shown in the steering table (shown in quarter-second intervals):

The corresponding graph is shown below:

Here we see an animation showing the vehicle positions in 1 second increments:

Now, suppose we start sequence entry 3 just 3 seconds after entry 2 begins. 
This means, although we specified that sequence entry 2 has 5 seconds to complete the steering input going from 0 degrees to +30 degrees, we did not give adequate time for this input to be completed. At the start of sequence 3, you will see the front wheels change from whatever angle the wheels are at when sequence 3 starts (in this case +18 degrees at time = 5 seconds) to 30 degrees instantly. The wheels will then steer from +30 degrees to -20 degrees as prescribed by the steering time of sequence 3. 

This situation is shown in tabular form below:

The corresponding graph can be found below:

The corresponding animation is shown here:

When manipulating fast control icons, one must of course be mindful of the implied time and steering time for the corresponding sequence entries. In this example below, the "I" icon is manipulated backward such that sequence entry 3 begins well before the sequence 2 steering input has been completed.

Recall the steering time can be controlled interactively by adjusting the length between the "I" icon and the steering wheel fast control icon. 

Tags: Steering, steering time, time, how to control steering, what is steering time, what is steering angle.

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