European Journal of Control (2005)11:80–81 # 2005 EUCA Discussion on: ‘‘Combined Adaptive Controller for UAV Guidance’’ Alexander Stotsky Department 92542, Engine Design and Development, Volvo Car Corporation, HB1S, SE-405, 31 Gothenburg, Sweden Combined algorithms that include both variable structure system and identification approaches are proposed in this paper for guidance of UAV. The approach is based on the application of the so called ‘‘shunt’’ – parallel feedforward compensator. A sim- ilar approach based on the feedforward compensator for stabilization of plants of any relative degree was proposed by Bartolini et al. [1]. It is recommended that this paper [1] be refered when considering the contribution of the paper under discussion. Applica- tion of the ‘‘Feedback Kalman–Yakubovich Lemma’’ [9] for design of the adaptive controller based on the parallel feedforward compensator is the contribution of the paper under discussion with respect to [1]. The contribution of the paper under discussion with respect to [4] is marginal. As can be seen from Figs 7 and 8 the adjustable parameters converge to their true values. The con- vergence of the parameters to their true values is achieved under the condition of the persistency of excitation. A mathematical proof that the regressor is persistently exciting could be a subject of further research. Reference 1. Bartolini G, Ferrara A, Stotsky A. Stability and exponential stability of an adaptive control scheme for plants of any relative degree. IEEE Trans Autom Contr 1995; 40(1): Discussion on: ‘‘Combined Adaptive Controller for UAV Guidance’’ Antonios Tsourdos and Brian A. White Guidance & Control Group, Department of Aerospace, Power and Sensors, Cranfield University, Shrivenham, Swindon SN6 8LA, UK The paper by Alexander Fradkov and Boris Andrievsky presents a design approach for an inte- grated guidance and autopilot for an unmanned aerial vehicle. For the autopilot it is proposed an adaptive control law scheme, using both variable structure and parameter identification approaches. The adaptive controller design is based upon shunting method and passification with feedback Kalman– Yakubovich lemma (FKYL). The adaptation control law is an internal part of the subordinate control system. The main loop of the considered system is timedependent. The control action in this loop is the reference signal for the internal adaptive controller. The adaptation algorithm provides the prescribed dynamic properties of the internal system when the UAV model parameters are changed in the wide range. E-mail: astotsky@volvocars.com