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Analysis of Basic PMP Solution

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1 Analysis of Basic PMP Solution
Find control u(t) which minimizes the function: 𝐽 π‘₯,𝑒 = 0 𝑇 𝐿 π‘₯,𝑒 𝑑𝑑 + 𝑉 π‘₯ 𝑇 x(t=0) = x0, T fixed, π‘₯ =𝑓(π‘₯,𝑒) To find a necessary condition to minimize J(x,u), we augment the cost function with the dynamics constraints 𝐽 π‘₯,𝑒,πœ† = 𝐽 π‘₯,𝑒 + 0 𝑇 πœ† 𝑇 (𝑓 π‘₯,𝑒 βˆ’ π‘₯ )𝑑𝑑 = 0 𝑇 𝐻 π‘₯,𝑒 βˆ’πœ† 𝑇 π‘₯ 𝑑𝑑 +𝑉(π‘₯ 𝑇 ) Extremize the augmented cost w.r.t. variations dx(t); du(t); dl (t); 𝛿 𝐽 = 0 𝑇 πœ•π» πœ•π‘₯ +πœ† 𝑇 π‘₯ 𝛿π‘₯ + πœ•π» πœ•π‘’ 𝛿𝑒+ πœ•π» πœ•πœ† βˆ’ π‘₯ 𝑇 π›Ώπœ† dt + πœ•π‘‰ πœ•π‘₯ βˆ’ πœ† 𝑇 𝑇 𝛿π‘₯ 𝑇 + πœ† 𝑇 0 𝛿π‘₯ 0 𝐻 π‘₯,𝑒 ≑𝐿 π‘₯,𝑒 +πœ† 𝑇 𝑓(π‘₯,𝑒)

2 Dimension of PMP Solution
Unknowns n state variables x(t) n co-state variables πœ†(t) m control variables u(t) Optimal control satisfies: π‘₯ = πœ•π» πœ•Ξ» 𝑇 =𝑓(π‘₯,𝑒) π‘₯ 0 = π‘₯ 0 n o.d.e.s with I.C.s 2 point B.V. problem βˆ’Ξ» = πœ•π» πœ•π‘₯ 𝑇 Ξ» 𝑇 = πœ•π‘‰ πœ•π‘₯ π‘₯ 𝑇 n o.d.e.s with T.C.s πœ•π» πœ•π‘’ =0 ; m algebraic equations

3 Additional Constraints?
Example: what if final state constraints fi(x(T))=0, i=1,…,p are desired: Add constraints to cost using additional Lagrange multipliers Multipliers π½π‘Ž π‘₯,𝑒 = 0 𝑇 𝐿 π‘₯,𝑒 𝑑𝑑 + 𝑉 π‘₯ 𝑇 𝑣 1 πœ‘ 1 π‘₯ 𝑇 + …+ 𝑣 𝑝 πœ‘ 𝑝 π‘₯ 𝑇 Cost augmentation Extremizing the constrained, augmented the cost function yields π‘₯ = πœ•π» πœ•Ξ» 𝑇 =𝑓(π‘₯,𝑒) π‘₯ 0 = π‘₯ 0 n o.d.e.s with I.C.s βˆ’Ξ» = πœ•π» πœ•π‘₯ 𝑇 Ξ» 𝑇 = πœ•π‘‰ πœ•π‘₯ (π‘₯ 𝑇 )+ πœ•πœ‘ πœ•π‘₯ (π‘₯ 𝑇 ) 𝑣 n o.d.e.s with T.C.s πœ•π» πœ•π‘’ =0 ; m algebraic equations πœ‘ 1 π‘₯ 𝑇 =0; …; πœ‘ 𝑝 π‘₯ 𝑇 =0 p algebraic equations

4 Additional Constraints?
Example: what if final time is undetermined? Final time T is an additional variable H(T) = 0 gives one additional constraint equation!


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