## 9 Conclusions
* For a fixed number of beams, measurement/generator speed error is lower with a pulsed lidar, measuring at multiple range gates. * Of all the realistic scan patterns investigated, the circularly-scanning continuous wave lidar yields the lowest measurement/generator speed error. For minimizing generator speed error, the optimal scan parameters for this scan pattern consist of a scan radius of 60% of the rotor radius and preview distance of 60% of the rotor diameter of the 126 m-rotor diameter NREL 5 MW reference turbine (resulting in a focus distance of 84.5 m and a cone angle of 26.6\({}^{\circ}\)). * The optimal scan parameters for the 4-beam pulsed lidar configuration, combining measurements from multiple ranges, consist of a scan radius of 85% rotor radius and preview distance of 110% rotor diameter for the farthest range gate, yielding a cone angle of 21.1\({}^{\circ}\). It should be noted, however, that, while minimizing measurement error is an important objective, it is not the only objective that should be considered. For example, a lidar with a suboptimal scan pattern but very high availability and reliability may be more useful than a lidar with an optimal scan pattern but lower availability. This further highlights the need for a systems engineering approach to lidar optimization for control applications. The steps involved in the design of a feedforward pitch controller for rotor speed regulation were described, illustrating how lidar measurements should be filtered and delayed properly to maximize the controller effectiveness. Through time domain simulations, it was shown that the rotor speed regulation achieved by the controller matches the value predicted by the theoretical frequency domain model. Finally, there are many promising directions that lidars for control applications could take in the future. For example, the design of LAC scenarios for extreme event detection is gaining importance. Additionally, new approaches to wind field estimation, such as the coupling of raw lidar measurements with fluid dynamics models, are being explored. Finally, it is anticipated that a modular lidar design philosophy will be adopted to address the variety of lidar system requirements for different control applications. [PERSON] organized the writing of this paper and wrote the Abstract, Introduction, Sections 2, 5 and 6, as well as the Conclusions. [PERSON] wrote Sections 3 and 4, in part using information from the Workshop meeting minutes prepared by [PERSON], as well as Section 8. Section 7 was written jointly by [PERSON], [PERSON] and [PERSON]. The authors all contributed to the planning, execution, and followup activities of the IEA Wind Task 32 Workshop \"Optimizing Lidar Design for Wind Turbine Control Applications,\" which was led by [PERSON] [PERSON] organized the first exercise of the workshop, on which much of Section 6 is based. [PERSON] and [PERSON] prepared and led the second exercise of the workshop, from which much of the material in Section 7 is drawn. The work performed by [PERSON] and [PERSON] was partially funded by the German Federal Ministry for Economic Affairs and Energy (BMWi) in the framework of the German joint research project ANWIND. [PERSON] acknowledges support from IEA Wind Task 32. Additionally, IEA Wind Task 32 is acknowledged for supporting the workshop \"Optimizing Lidar Design for Wind Turbine Control Applications\" in Boston, MA (July 2016), which served as the foundation for this work. Finally, the publication of this work was supported by Envision Energy USA, Ltd.  
**Acknowledgments:** The authors thank the participants of IEA Wind Task 32 Workshop \"Optimizing Lidar Design for Wind Turbine Control Applications\" for their contributions to the workshop, including presentations and input during group discussions, which were incorporated into this paper. Thirty-three participants attended the workshop, representing lidar suppliers, wind turbine manufacturers, academia, and the research community. **Conflicts of Interest:** The authors declare no conflict of interest.