Morten Ottestad

Bio: Morten Ottestad is an academic researcher from University of Agder. The author has contributed to research in topics: Coalescence (physics) & Centrifugal pump. The author has an hindex of 6, co-authored 12 publications receiving 131 citations.

Multicopter UAV design optimization

Abstract: Designing and selecting hardware for a multirotor can be challenging in order to get the best flight performance out of the system. In addition to selecting the hardware, the number of actuators can also be altered. For a 4 actuator (quadrotor) setup, one set of hardware can give the optimal design, while for a 6 actuator setup (hexarotor) the same hardware may not necessarily give the same response. In this paper we present a design optimization process of a multirotor, where the hardware is selected from a set of low-cost off-the-shelf standard RC hobby parts. Constraining the problem to a given hardware ensures existence of the selected hardware, and the design can be implemented. Also the system equations will remain linear when selecting from a set of given data. Hence the problem is defined as a mixed integer linear program (MILP) and solved with the Cplex solver. The Cplex solver is fast and the solution is close to the optimal solution of the problem. In this paper the multirotor is designed for 4, 6 and 8 actuators, and the design with the lowest value of the objective function is the optimal design. As shown, optimizing the design for a given set of hardware and payload results in a 11 minutes longer time of flight, than just using the biggest propeller, motor and battery available.

Multicopter Design Optimization and Validation

Abstract: This paper presents a method for optimizing the design of a multicopter unmanned aerial vehicle (UAV, also called multirotor or drone). In practice a set of datasheets is available to the designer for the various components such as battery pack, motor and propellers. The designer can not normally design the parameters of the actuator system freely, but is constrained to pick components based on available datasheets. The mixed-integer programming approach is well suited to design optimization in such cases when only a discrete set of components is available. The paper also includes an experimental section where the simulated dynamic responses of optimized designs are compared against the experimental results. The paper demonstrates that mixed-integer programming is well suited to design optimization of multicopter UAVs and that the modeling assumptions match well with the experimental validation.

Experimental validation of a quaternion-based attitude estimation with direct input to a quadcopter control system

Abstract: This paper presents a method to calculate the attitude quaternion of a quadcopter with few calculations. The quaternion calculation is based on accelerometers and gyroscopes from an Inertial Measurement Unit (IMU). The quaternion from the accelerometer is calculated as the shortest rotation arc from the gravity vector in the navigation frame. The quaternion from the gyroscope is calculated based on equations of the quaternion derivative. A complementary filter is combining the two quaternions with a componentwise comparison. The attitude estimation is calculated without any trigonometric functions. The quaternion is directly used as an input to the attitude controller. The attitude controller is a PD controller running at 400Hz. A model of the quadcopter in Matlab verified that the control system worked as intended. The estimator was verified with a Stewart platform, by mounting the quadcopter on top of it and comparing the angles from the Stewart platform with the angles from the filter. Finally the algorithms were implemented on a quadcopter controller board, and the attitude estimator were compared with the attitude estimation from a high-end IMU from MicroStrain. The complete control system was also tested on a 8-bit microcontroller running at 16 MHz. The relatively slow processor on the microcontroller was also able to do every calculations within 2.5ms.

Reducing the static friction in hydraulic cylinders by maintaining relative velocity between piston and cylinder

Abstract: This paper is concerned with friction in hydraulic cylinders and it's influence on the performance of hydral-ically actuated system. A method for the elimination of stiction in hydraulic cylinders is presented and experimentally verified. The method utilizes the rotational degree of freedom between the piston and the cylinder to add relative velocity at the contact surfaces between piston and cylinder when the main axial motion is zero. For modeling purposes an augmentation of the Stribeck friction force equation is introduced that reflects the influence of the added motion. The possible impact of stiction elimination on the performance of heave compensation equipment is discussed and examplified via time domain simulations.

Robust adaptive backstepping control design for a Nonlinear Hydraulic-Mechanical System

Abstract: The complex dynamics that characterize hydraulic systems make it difficult for the control design to achieve prescribed goals in an efficient manner. In this paper, we present the design and analysis of a robust nonlinear controller for a Nonlinear Hydraulic-Mechanical (NHM) System. The system consists of an electrohydraulic servo valve and two hydraulic cylinders. Specifically, by considering a part of the dynamics of the NHM system as a norm-bounded uncertainty, two adaptive controllers are developed based on the backstepping technique that ensure the tracking error signals asymptotically converge to zero despite the uncertainties in the system according to the Barbalat lemma. The resulting controllers are able to take into account the interval uncertainties in Coulomb friction parameters and in the internal leakage parameters in the cylinders. Two adaptation laws are obtained by using the Lyapunov functional method and inequality techniques. Simulation results demonstrate the performance and feasibility of the proposed method.

Decoupled Modeling and Nonlinear Speed Control for Five-Phase PM Motor Under Single-Phase Open Fault

Abstract: Fault-tolerant control of a five-phase (5Ph) permanent magnet (PM) motor has been recently widely studied, however decoupled modeling under faulty conditions is discussed in less details. In this paper, decoupled model of the 5Ph PM motor under single-phase open fault is investigated and based on the proposed model field oriented control (FOC) is applied to the motor. The proposed model is based on the concept of preserving values of fundamental magnetic motive force (MMF) and back electromotive force (EMF) under single-phase open fault, the same as in healthy case, along with keeping equal torque equation at fundamental rotating space. Nevertheless, the output torque still presents some noises due to third harmonics of air-gap flux and system uncertainties, and to cope with those disturbances, sliding mode control (SMC) is proposed in the speed loop to improve the speed performance. The proposed SMC contains a PI controller and a chattering term, and thus it can be easily tuned. The decoupled model is verified by transient finite element analysis finite element analysis (FEA) and further experiment results are presented to confirm the effectiveness of the proposed control strategy.

A Practical Performance Evaluation Method for Electric Multicopters

Abstract: Multicopters are attracting more and more attention these years. In the design stage, designers and users wonder if an assembled multicopter can meet their performance requirements, such as hovering endurance, system efficiency, maximum load, maximum pitch, and maximum flight distance. However, in practice, they used to evaluate the performance of a multicopter through lots of flight experiments or by experience, which are normally inefficient and costly. This motivates us to propose a comprehensive offline evaluation algorithm of multicopter performance. The performance indices considered are mainly determined by the propulsion system, including motors, propellers, electronic speed controllers, and batteries. Therefore, in the first stage of this research, models are established for the components of a propulsion system. In order to facilitate the application, only technical specifications of components offered by manufacturers are required as the input of the models. Based on the models and their relationships, equations describing performance indices are established and then solved to perform the evaluation. Finally, several examples are given to demonstrate the efficiency of the proposed evaluation method. As a result, a website ( www.flyeval.com ) is established, which can provide users with the performance evaluation mentioned in this paper.

A compound control strategy combining velocity compensation with ADRC of electro-hydraulic position servo control system.

Abstract: In order to enhance the anti-jamming ability of electro-hydraulic position servo control system at the same time improve the control precision of the system, a compound control strategy that combines velocity compensation with Active Disturbance Rejection Controller (ADRC) is proposed, and the working principle of the compound control strategy is given. ADRC controller is designed, and the extended state observer is used for observing internal parameters uncertainties and external disturbances, so that the disturbances of the system are suppressed effectively. Velocity compensation controller is designed and the compensation model is derived to further improve the positioning accuracy of the system and to achieve the velocity compensation without disturbance. The compound control strategy is verified by the simulation and experiment respectively, and the simulation and experimental results show that the electro-hydraulic position servo control system with ADRC controller can effectively inhibit the external disturbances, the precise positioning control is realized after introducing the velocity compensation controller, and verify that the compound control strategy is effective.

Multicopter UAV design optimization

Abstract: Designing and selecting hardware for a multirotor can be challenging in order to get the best flight performance out of the system. In addition to selecting the hardware, the number of actuators can also be altered. For a 4 actuator (quadrotor) setup, one set of hardware can give the optimal design, while for a 6 actuator setup (hexarotor) the same hardware may not necessarily give the same response. In this paper we present a design optimization process of a multirotor, where the hardware is selected from a set of low-cost off-the-shelf standard RC hobby parts. Constraining the problem to a given hardware ensures existence of the selected hardware, and the design can be implemented. Also the system equations will remain linear when selecting from a set of given data. Hence the problem is defined as a mixed integer linear program (MILP) and solved with the Cplex solver. The Cplex solver is fast and the solution is close to the optimal solution of the problem. In this paper the multirotor is designed for 4, 6 and 8 actuators, and the design with the lowest value of the objective function is the optimal design. As shown, optimizing the design for a given set of hardware and payload results in a 11 minutes longer time of flight, than just using the biggest propeller, motor and battery available.

PID and Fuzzy-PID Control Model for Quadcopter Attitude with Disturbance Parameter

Abstract: This paper aims to present data analysis of quadcopter dynamic attitude on a circular trajectory, specifically by comparing the modeling results of conventional Proportional Integral Derivative (PID) and Fuzzy-PID controllers. Simulations of attitude stability with both control systems were done using Simulink toolbox from Matlab so the identification of each control system is clearly seen. Each control system algorithm related to roll and pitch angles which affects the horizontal movement on a circular trajectory is explained in detail. The outcome of each tuning variable of both control systems on the output movement is observable while the error magnitude can be compared with the reference angles. To obtain a deeper analysis, wind disturbance on each axis was added to the model, thus differences between each control system are more recognizable. According to simulation results, the Fuzzy-PID controller has relatively smaller errors than the PID controller and has a better capability to reject disturbances. The scaling factors of gain values of the two controllers also play a vital role in their design.