I want to control the lateral dynamics of a car like ground vehicle for implementing automatic behavior (such as lane change, side slip control). please suggest me how to find or develop a steering actuator model in terms of state space or transfer function. How to design a genuine actuator for steering?
Any help will be appreciated.
You can estimate the model parameters like in "Advances in Automotive Control 1995" if you have performed required measurements.
But on the other hand, actuator dynamics are often neglected in traction/steering control.
Hello,
general dynamics pulling a vehicle model ( eg bicycle ), this validation model is followed by the synthesis model that serves as a means to analyze the system. Knowing that the control law we generally provides information on the forces to be applied (in Newton ), the actuator then is generally characterized by a constant that uses a conversion means. But on the other hand, in the actual application (eg electric actuator ) , take into account the dynamics of the actuator seen to make him a control loop of electric current, which protect it from current peaks.
The steering system of a car is not an under actuated system hence transfer function implementing a PID could suffice.
Though there are techniques of modelling of actuator, but as your main objective is to control the dynamics of car, you need not to know model of steering actuator. First of all you must know the dynamics of ground vehicle. According to your control objective you design a control technique, you damp it in controller, on the basis of control algorithm controller gives output to the steering actuator in voltage. The relation between voltage and steering is given in the data-sheet of a particular actuator. Later you can set the voltage of controller according to your steering demand. Once i used the same procedure for controlling passenger car and it worked.
I agree with the answers given by N. Sharma and D.S. Pranav.
A very simple first order model can be introduced to simulate the time lag between the desired steering angle and the real steering angle. The transfer function describing this time lag is H(s) = 1/(k*s+1) (in the Laplace domain), where 'k' is the time constant. The input for this transferfunction X(s) is f.e. the desired steering angle, the output Y(s) will be the real steering angle.
Y(s) = H(s)X(s)
I also agree with the answers given by D. S. Pranav, N. Sharma and L. Keersmaekers.
the steering actuator model can be represented by a conventional system of the first or second order maximum and identification of the parameters of this model can be made by experimental methods.
I think maybe using system identification techniques could be very useful for this problem while they could be used in online control approaches. First of all you have to estimate that the system is static or dynamic then investigates the linearity of the system. There are many ways for identification which are based on the inputs and measured outputs of the system. Also you can use SI toolbox of the Matlab.
Obtaining exact model could be really challenging if you have no idea about the system and you have to try all the different ways of identification toward extracting the exact model.
After obtaining the model any controller could be used. If you use an identification method while controlling a model with any control law it is regarded as an adaptive controller.
I suppose introduce a first order transfer function that provides a reasonable delay will do
Hi Sharmin
You can check the report
Automatic Steering Methods for Autonomous Automobile Path Tracking
in the following link
https://www.ri.cmu.edu/pub_files/2009/2/Automatic_Steering_Methods_for_Autonomous_Automobile_Path_Tracking.pdf
The control engineers usually neglect the actuator dynamics. However if you are interested then pick any of the actuators (used for steering control).
Regarding the model there are two main concerns 1) its structure and 2) ITS parameters.
The model structure of any actuator can be found in the rich literature of automotive but for parameters you have to perform experiments.
Check this links the articles maybe help you
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.360.9295&rep=rep1&type=pdf
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.430.4066&rep=rep1&type=pdf
https://www.researchgate.net/profile/Marek_Stania/publication/235950779_Mechatronics_Systems_of_Autonomous_Transport_Vehicle/links/551a3ba30cf244e9a4585701.pdf
https://pdfs.semanticscholar.org/6e71/ad6c2e64bb70ea0556590ec0d26c0ba6e943.pdf
https://diginole.lib.fsu.edu/islandora/object/fsu:181632/datastream/PDF/view
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