Trading output performance for input allocation: application to the JET tokamak shape controller

In this paper we revisit the dynamic allocation scheme for input redundant plants proposed in [L. Zaccarian, 2009] within a set-point regulation setting and propose generalizations that apply to cases where the plant under consideration is not input redundant but the control specifications allow to modify the set-point regulation within certain bounds. In this case, the input allocator is extended to the nonredundant case by allowing it to improve the input allocation selection at the price of some output regulation error. Similar to [L. Zaccarian, 2009], the allocator behaves according to some dynamics that converges to the minimum of a certain cost function. The allocation scheme is applied to the JET tokamak shape controller by illustrating its capabilities to enforce coil currents selections that tend to move away from the saturation limits within the allowable degrees of freedom. The allocator behavior is illustrated by simulation on the JET tokamak both in off-line operation (in open loop during the pulse planning phase) and in on-line operation (in closed loop during the pulse).