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Questions related from Saeb AmirAhmadi Chomachar
PID controller is reportedly widely built and used in control systems engineering for industrial applications. The PID-controller has a transfer function as: (Kd*s^2+Kp*s+Ki)/s. Therefore, it...
09 November 2020 8,255 10 View
We all have been accustomed to see a block diagram for a linear control system, where in the forward path, first sits the controller, then actuator, and then plant. What if we flip the blocks of...
06 October 2020 9,805 21 View
We all have been accustomed to design a controller with negative feedback loop. I have read in some texts as Ogata control engineering book that, positive feedback loops are more satisfying than...
06 October 2020 9,046 58 View
Can you propose two functions of totally different expressions in x, but exactly the same numerical value when plotted? I mean two functions; y1=f1(x), and y2=f2(x), which are totally of...
25 September 2020 9,372 4 View
I have developed a paper on modified Newtonian dynamics, and in some aspects, it is related to foundations of physics and mechanics. Please recommend me a journal, where I can get a peer-review of...
03 April 2020 8,544 0 View
The brachistochrone is a well-known problem in calculus of variations and optimal control. I ask if there is any explicit solution to the problem?. In the existing texts, x and y are usually...
01 March 2020 842 5 View
For a linear damped system; xdot=-k*x, the solution is x=x0*e^(-kt), hence the system is of exponential dissipation rate. But what can we say about some other systems, for example; xdot=-k*x^3?...
12 December 2019 8,425 0 View
I've heard some researchers say Newton's second law of motion if to be tested near the earth surface could possibly fail. But what is the glitch of the Newtonian dynamics, possibly for a falling...
11 November 2019 1,709 3 View
It seems the state evolution ode; xdot=f(x,u), is known to satisfy f(0,0)=0, hence f(0,u(0))=0, then can we conclude at any control system, always u(0)=u(x=0)=0, and get the result that...
20 September 2019 3,130 3 View
Assume we have a control system in state space as: xdot1=u1, xdot2=u2, where x is state and u is control. I am interested to know the possibility of complex valued control signal to control such...
28 August 2019 7,376 3 View
please catch a glimpse on the pdf attached to this question, and let me know, how to plot the surface of value function v(x,u,t). Please also remind me what are the names of coordinate system on...
17 April 2019 6,069 1 View
I am interested to know, why is control set in control systems theory, usually assumed convex, more specifically, a convex cone, a convex hull or a convex set? Please let me know if you've gotten...
25 March 2019 7,552 4 View
please let me know, the assumptions over the Lagrangian function included into optimal cost functional. I want to know, if Lagrangian (in control terminology, NOT optimization), is convex in...
20 February 2019 5,851 5 View
I've read through the existing research that, NASA has been trying to build a hypersonic aircraft, however, the attempts all have failed during too many decades. I am interested to know, what the...
17 October 2018 2,193 15 View
I am to know what is the difference of using tensor strain (particularly its rate) and engineering strain-rate for two dimensional fluid flow analysis. As you may know, the Navier-Stokes momentum...
17 August 2018 5,862 4 View
Assume: du= f1(u,v).dx+f2(u,v).dy (1) dv= g1(u,v).dx+g2(u,v).dy (2) f1,f2, and, g1,g2 are continuous and known functions. We know further that implicitly h(u,v)=0 and hence we...
26 July 2018 6,573 9 View
I want to have insight over fluid-flow vector field, as I have an ordinary differential equation (ode): dv/du=-2(u2+v2)/(v2 - 5u2) where u and v are horizontal and vertical velocity components...
25 July 2018 5,129 5 View
As I know, the ordinary differential equation (ODE), xdot= -x^3+u, where x is the state variable, and u the control variable, is the control system associated to a falling object in atmosphere...
25 June 2018 8,221 99 View
As I know, boundary-layer is formulated for semi-infinite flat plate with zero incidence (the Blasius ode). If the incidence of plate is not zero then it is named wedge flow, mathematically...
07 June 2018 3,238 12 View
From fluid dynamics, I know boundary-layer is an imaginary hypothesis, adopted for finding velocity profile over flat plate. But what is boundary-layer suction?! How can we modify a hypothetical...
06 June 2018 9,373 11 View
I think Lift force acting on an airfoil is calculated as L=1/2 CL ρ V∞2 , where ρ is the air density and V∞ the free upstream flow velocity. But this is calculated using Lift coefficient CL, which...
06 June 2018 2,401 10 View
I know for boundary-layer, adverse pressure gradient (dp/dx>0) is a necessary condition for flow separation. Also, when the wall-friction becomes zero ( τw=µ ∂u/ ∂y=0) , the flow separates, and...
06 June 2018 3,802 15 View
It is also found that a flow in a pipe is laminar if the Reynolds Number (based on diameter of the pipe) is less than 2100 and is turbulent if it is greater than 4000. I want to know: how are...
05 June 2018 3,455 20 View
I have evidence that, too many global researchers belong to research secro-society. As they belong to this secret scientific community, they surreptitiously promote their colleague members and...
27 May 2018 4,609 16 View
I need an article with a literature survey on contributions over large-strain (finite-strains) or similar continuum topics.
05 May 2018 10,127 5 View
The Laplace equation for potential function in fluid flow is formulated as: Δ ϕ (x,y)=0, where Δ is the Laplacian operator. I want to know what does happen to the solution when ϕ and vector-field...
26 April 2018 1,728 11 View
I am to numerically calculate the value of cost, for a certain optimal quadratic regulator. Cost in quadratic regulator is J=J(t)= int((x^2+u^2).dt, 0...inf). I have the numerical values of x and...
29 January 2018 5,581 1 View
I am wondering to enforce state dissipation to stabilize nonlinear or linear systems. Assume a nonlinear control system as xdot=-x3+u. Then to forcefully dissipate x as exponentially by setting: x...
24 January 2018 1,716 16 View
I am looking to discuss here, about the sign (direction) of skin-friction at wall (wall shear-stress), at boundary-layer over flat plate with zero incidence. Is it in direction of the moving...
14 January 2018 5,485 28 View
We know that Kalman filter is not available for nonlinear systems, hence, extended Kalman filter (EKF) was developed as an alternative. Similarly, unscented Kalman filter (UKF) is an alternative...
11 November 2017 6,578 9 View
What's your idea about stabilizability and controllability and particularly their interconnection? How do you correspond them together? What's your immediate conclusion about the research paper...
31 October 2017 2,997 11 View
I need to evaluate inverse Laplace-transform of sinh (s), or cosh (s). s is the Laplace-transform variable. Is there any tabular formula for that? Matlab and Maple do not yield the solution.
09 September 2017 7,521 12 View
F''(t)-(1/4/pi/T)*F0*F'(t)-(6/T^2)F(t)=0. If T approaches infinity then: Am I allowed to write the equation...
06 September 2017 2,923 36 View
I want to design a missile with tails while controlled with canard fins. The question is how to make the missile of critical damping in its pitch-mode response to the elevator (actuator-fin)...
05 April 2017 7,509 2 View
Please have a look at the image attached to this query, then let me know which of the five possible aerodynamic surface control setup is suitable for a rolling-airframe missile (spinning missile)?...
25 March 2017 7,597 3 View
Is it possible to use a symmetric diamond (double-wedge) airfoil instead of a cambered airfoil in missiles moving at subsonic speed?
12 March 2017 1,264 12 View
Certainty equivalence property (CEP) is another name for model-predictive control (MPC). Based on CEP, it does not differ whether you include additive noise into calculation or not. It means it...
01 January 1970 5,326 6 View
I think there is no constant velocity in our every-day engineering problems. Even a car moving with a seemingly constant velocity, has too many low-amplitude diminutive changes in its velocity,...
01 January 1970 9,131 5 View
Perron's paradox, emphasizes the danger of assuming a solution to a mathematical problem exists, if the solution is actually nonexistent. For example, if we assume the largest natural number...
01 January 1970 1,101 3 View
Have you ever wondered about using dimensional analysis in mathematics, as we do in physics. For example, the Pythagoras formula is: a^2+b^2=c^2 which relates the surface areas of squares...
01 January 1970 1,751 3 View
As the name implies, "gain-scheduling" is to schedule the gains of a controller to account for changes in system dynamics that happen through state-space evolution due to disturbance or...
01 January 1970 3,006 3 View
I've contemplated an idea, to implement PID controller as an electronic circuit, attached as an illustration here. This is only a raw idea. I know there should be some Earth branches, but I'm not...
01 January 1970 1,098 4 View
The Laplace-transform is defined by the integral: F(s)=L{f(t)}=integrate(exp(-st)*f(t)*dt, t=0...∞). It is interesting to spot that, the following integral has the same numerical value in...
01 January 1970 4,079 9 View
Control Lyapunov function (CLF) methodology tries to minimize a quadratic cost-function as; V(x)=x^2, through a point-wise setup. However, optimal control minimizes a quadratic cost-function...
01 January 1970 688 3 View
Is there any direct correspondence between delay and error? If yes, how we can benefit from one to recompense for the other? I am waiting for your viewpoints to discuss this subject. Thanks.
01 January 1970 3,433 4 View
Please feel free to share your knowledge about intuitive examples for offset function in optimal cost functional. I've illustrated one of the case examples, attached here.
01 January 1970 10,015 0 View
