Real-time estimates of weight and mass center location for helicopters are desirable for flight control and condition-based maintenance purposes. While methods to estimate mass parameters of helicopters have been developed, they often assume near-perfect knowledge of helicopter dynamics and have been validated only through simulated measurement data. The work described here aims to experimentally validate a method for weight and mass center estimation using an ALIGN T-REX 600e R/C helicopter. The estimation algorithm utilizes an extended Kalman filter (EKF) which estimates the helicopter states along with the weight and mass center location in real-time. Nonlinear system identification is performed using maximum likelihood estimation to create an accurate dynamic model for use in the EKF. Results show that given a reasonably accurate dynamic model, weight, stationline mass center location, and buttline mass center location can be reliably estimated in non-descending flight conditions. Weight estimation is shown to be robust to sudden weight changes during flight, whereas stationline and buttline mass center estimates are marginally robust to sudden shifts in the mass center location. Waterline mass center proved to be unobservable for the axial flight maneuvers conducted. Detailed flight test studies characterize estimation error in weight and three-dimensional mass center position using the EKF formulation.

This study proposes an application design for Stewart platform. The Stewart platform is selected to function as a mass center adjusting mechanism. The mechanism is attached to the chassis of a coaxial two-wheeled self-balancing car so that the mass center of the car can be shifted backward and forward to change the car speed. Besides, the mechanism can be applied to adjust the contacting forces between wheels and the ground if the mass center is shifted to the left and right of the car. In order to verify the feasibility of the design, the dynamic behavior of the car and the designing requirements for the Stewart platform are examined by using dynamic simulations on both sagittal plane and coronal plane. Therefore, the equation of motion of the car is derived from Lagrange mechanics. The driving torques to the wheels for balancing control, velocity control, and direction control are all determined by PID controllers. An algorithm for determining the displacement, that the mass center should be shifted to prevent losing contact force between wheels and the ground, is also introduced. The results of dynamic simulation show that the proposed application is feasible. Designing requirements for synthesizing the dimensions of the adjusting mechanism are also determined from the simulations. Finally, the dimensions of the desired Stewart platform are determined according to the designing requirements. The workspace of the Stewart platform is then investigated by inversed kinematic analysis method. Since the workspace includes the necessary space for the proposed application, which means the specified dimensions of the Stewart platform is valid.

The aim of this thesis is to develop a methodology for obtaining mass properties of a vehicle using specific test rig. Investigated mass properties are the mass, location of center of gravity and the inertia tensor. Accurate measurement of mass properties of vehicles is crucial for vehicle dynamics research. The test rig consists of a frame on which the vehicle is fixed and which is suspended from the ceiling of the laboratory using steel cables. Mass and location of center of gravity are measured using the data from the test rig in equilibrium position and basic static equations. Inertia tensor is measured using the data from dynamical response of the system. For this purpose an identification routine which employs prediction error method is developed using the built&ndash / in functions from the System Identification Toolbox of MATLAB&reg / . The experiment was also simulated using Simmechanics Toolbox of MATLAB&reg / . Identification code is verified using the results of the experiment simulations for various cases.