a time (t5) got back from a time (t6)

11:52 Nov 13, 2018 

Oh dear!
Looks like you've got a tough job on your hands!
The use of 'delta' t for a duration cinfirms my suspicions that 't' on its own is an instant in time.
And also, I suspect that –900 is probably an error for –90°.

11:08 Nov 13, 2018 

I also think that the term is incorrect hence the reason for my question. hereafter more explanation.
A driver starts to rotate a steering wheel to the left (θ<00) at a time t1, and steers it to about -900 at a time t2. Subsequently, the driver starts to rotate the steering wheel to the right at a time t3, and returns it to the neutral position (θ=00) at a time t4. Then, the driver leaves his/her hands off from the steering wheel at a time t5, so that the steering wheel is returned by Δθ due to the residual distortion energy of tires.
The steer angle θ is compensated as explained below. The steer angle θ at a time (e.g. a time t5) got back from a time (t6) when the step S804 is affirmed (the torque value is smaller than the predetermined value for the certain period of time ) by a predetermined time duration (Δt) is handled as a compensated steer angle θ. By using the steer angle θ at the previous time t5, the steer angle difference Δθ forcibly rotated due to the residual distortion energy can be compensated.

10:46 Nov 13, 2018 

It looks like you may have flawed EN in this codumnt! Ceratonly, "got back from" seems not only unusual EN, but curious in the register of a patent.
I think it needs to be read as 'obtained/derived from'— or possibly 'counted back from', but that would need extra context to confirm or not.