Stabilizing Ship Motion With a Dual System Inertial Disk

Norwegian industries are constantly assessing new technologies and methods for more efficient and safer maintenance in the aqua cultural, renewable energy, and oil and gas industries. These Norwegian offshore industries share a common challenge: to install new equipment and transport personnel in a safe and controllable way between ships, farms and platforms. This paper deploys the Moving Frame Method (MFM) to analyze ship stability moderated by a dual gyroscopic inertial device. The MFM describes the dynamics of the system using modern mathematics. Lie group theory and Cartan’s moving frames are the foundation of this new approach to engineering dynamics. This, together with a restriction on the variation of the angular velocity used in Hamilton’s principle, enables an effective way of extracting the equations of motion. This project extends previous work. It accounts for the dual effect of two inertial disk devices, it accounts for the prescribed spin of the disks. It separates out the prescribed variables. This work displays the results in 3D on cell phones. It represents a prelude to testing in a wave tank.

Modeling a Knuckle-Boom Crane Control to Reduce Pendulum Motion Using the Moving Frame Method

A Knuckle Boom Crane is a pedestal-mounted, slew-bearing crane with a joint in the middle of the distal arm; i.e. boom. This distal boom articulates at the ‘knuckle (i.e.: joint)’ and that allows it to fold back like a finger. This is an ideal configuration for a crane on a ship where storage space is a premium. This project researches the motion and control of a ship mounted knuckle boom crane to minimize the pendulum motion of a hanging load. To do this, the project leverages the Moving Frame Method (MFM). The MFM draws upon Lie group theory — SO(3) and SE(3) — and Cartan’s Moving Frames. This, together with a compact notation from geometrical physics, makes it possible to extract the equations of motion, expeditiously. The work reported here accounts for the masses and geometry of all components, interactive motor couples and prepares for buoyancy forces and added mass on the ship. The equations of motion are solved numerically using a 4th order Runge Kutta (RK4), while solving for the rotation matrix for the ship using the Cayley-Hamilton theorem and Rodriguez’s formula for each timestep. This work displays the motion on 3D web pages, viewable on mobile devices.

MoVE: A Mobility Virtual Environment for Autonomous Vehicle Testing

Autonomous vehicle researchers need a common framework in which to test autonomous vehicles and algorithms along a realism spectrum from simulation-only to real vehicles and real people. The community needs an open-source, publicly available framework, with source code, in which to develop, simulate, execute, and post-process multi-vehicle tests. This paper presents a Mobility Virtual Environment (MoVE) for testing autonomous system algorithms, vehicles, and their interactions with real and simulated vehicles and pedestrians. The result is a network-centric framework designed to represent multiple real and multiple virtual vehicles interacting and possibly communicating with each other in a common coordinate frame with a common timestamp. This paper presents a literature review of comparable autonomous vehicle softwares, presents MoVE concepts and architecture, and presents three experimental tests with multiple virtual and real vehicles, with real pedestrians. The first scenario is a traffic wave simulation using a real lead vehicle and 3 real follower vehicles. The second scenario is a medical evacuation scenario with 2 real pedestrians and 1 real vehicles. Real pedestrians are represented using live-GPS-followers streaming GPS position from mobile phones over the cellular network. Time-history and spatial plots of real and virtual vehicles are presented with vehicle-to-vehicle distance calculations indicating where and when potential collisions were detected and avoided. The third scenario highlights the avoid() behavior successfully avoiding other virtual vehicles and 1 real pedestrian in a small outdoor area. The MoVE set of concepts and interfaces are implemented as open-source software available for use and customization within the autonomous vehicle community. MoVE is freely available under the GPLv3 open-source license at gitlab.com/comperem/move.

Control Simulations for a Stewart Platform Compensator Mounted on Moving Base

In this paper, utilizing the analytical equations of motion for a base-moving Stewart platform, we design an active wave compensation system for a surgery table installed on the top plate of a Stewart platform in a ship. In our medical application, the base plate of a Stewart platform moves with the motion of the ship. For a base-moving Stewart platform, we presented analytical equations of motion in matrix form in the paper: IMECE2018-87253. The objective of the platform is to compensate the pitching, rolling, and heaving motions of the ship (with respect to an inertial coordinate system). As control methods for the nonlinear system, we employ a hybrid controller combining resolved acceleration control with H∞ control, and integral sliding mode control (ISMC). The ISMC with input time delay is also designed with a state predictor, which includes a ship motion predictor utilizing an autoregressive model. Finally, to assess the control performance and robustness for the system with uncertainties, numerical simulations are presented. In addition, the simulation results of the predictor based ISMC for the system with input time delay are illustrated showing the effectiveness of the controller.

On an Independent Period-1 Motion in a Flexible Rotor System

This paper investigates stable and unstable period-1 motions in a rotor system through the discrete mapping method. The discrete mapping of a nonlinear rotor system is for stable and unstable period-1 motions. The stability and bifurcation of periodic motions are determined. Numerical simulations of periodic motions are completed and phase trajectories, displacement orbits and velocity plane are illustrated. The period-1 motion near the internal resonance is determined with large vibration in the nonlinear rotor system.

Simultaneous and Iterative Estimation of Vehicle Ride Model States and Parameters

With advancements in vehicle electronics and growing focus on vehicle safety systems, state and parameter estimation has become a remarkable sphere of research. In this study, the vehicle vertical dynamics states and parameters were estimated simultaneously and iteratively with relevant vehicle responses. This was achieved through vehicle tests, designed to excite the corresponding vehicle states. A linear Kalman filter was used for state estimation. Vehicle parameters were obtained as a optimal solution using an optimization algorithm. With the help of multi-DOF vehicle ride model along with real vehicle measurements, the state and parameter estimators work concurrently to obtain the results. A cleat test was performed for a Sports Utility Vehicle (SUV) in IPG CarMaker® and in reality, for evaluation of the proposed framework. The state estimation results showed upto 93% correlation from simulated data and upto 81% correlation from real time measurements. Parameter estimation produced an average error of only 9.1%. This demonstrated the efficacy of the algorithm for use in vehicle systems.

Neural Network Based Fault Tolerant Control for a Semi-Active Suspension

In this study a Neural Network based fault tolerant control is proposed to accommodate oil leakages in a magnetorheological suspension system based in a half car dynamic model. This model consists of vehicle body (spring mass) connected by the MR suspension system to two lateral wheels (unsprung mass). The semi-active suspension system is a four states nonlinear model; it can be written as a state space representation. The main objectives of a suspension are: Isolate the chassis from road disturbances (passenger comfort) and maintain contact between tire and road to provide better maneuverability, safety and performance. On the other hand, component faults/failures are inevitable in all practical systems, the shock absorbers of semi-active suspensions are prone to fail due to fluid leakage but quickly detect and diagnose this fault in the system, avoid major damage to the system and ensure the safety of the driver. To successfully achieve desirable control performance, it is necessary to have a damping force model which can accurately represent the highly nonlinear and hysteretic dynamic of the MR damper. To simulate parameters of the damper, a quasi-static model was applied, quasi-static approaches are based on non-newtonian yield stress fluids flow by using the Bingham MR Damper Model, relating the relative displacement of the piston, the frictional force, a damping constant, the stiffness of the elastic element of the damper and an offset force. The Fault detection and isolation module is based on residual generation algorithms. The residua r is computed as the difference between the displacement signal of functional and faulty model, when the residual is close to zero, the process is free of faults, while any change in r represents a faulty scheme then a wavelet transform, (Morlet wave function) is used to determine the natural frequencies and amplitudes of displacement and acceleration signal during the failure, this module provides parameters to the neural network controller in order to accommodate the failure using compensation forces from the remaining healthy damper. The neural network uses the error between the plant output and the neural network plant for computing the required electric current to correct the malfunction using the inverse dynamics function of the MR damper model. Consequently, a bump condition, and a random profile road (ISO 8608) described by the power spectral density (PSD) of its vertical displacement, is used as disturbance of control system. The performance of the proposed FTC structure is demonstrated trough simulation. Results shows that the control system could reduce the effect of the partial fault of the MR Damper on system performance.

Integrated Optimization of Structure and Control in Ultra-Precision Motion Systems

Ever-increasing demands for precision and efficiency in ultra-precision motion systems will result in a lightweight and flexible motion system with complex dynamics. In this paper, a systematic approach is proposed where control gains, 3D structural topology and actuator configuration are integrated into optimization to derive a system-level optimal design which possesses a high vibration control performance, and still satisfies multiple design constraints. A material interpolation model with high accuracy is proposed for the integrated optimization, a simple integral equation utilizing R-functions and level-set functions is established to represent complex non-overlapping constraints of actuators. Over-actuation degrees are utilized to actively control the dominant flexible modes. Responses of residual flexible modes are restricted by increasing the coincidence of their nodal areas at actuators (sensors) locations. The objective function is the constructed worst-case vibration energy of the flexible modes. A dual-loop solving strategy combining the genetic algorithm and the modified optimal criteria method is adopted to solve the optimization problem. A fine stage in the wafer stage is designed to prove the effectiveness of the proposed method.

Amplitude-Frequency Response for Superharmonic Resonance of Fourth Order of Electrostatically Actuated MEMS Cantilever Resonators

This paper deals with the frequency response of superharmonic resonance of order four of electrostatically actuated MicroElectroMechanical Systems (MEMS) cantilever resonators. The MEMS structure in this work consists of a microcantilever parallel to an electrode ground plate. The MEMS resonator is elelctrostatically actuated through an AC voltage between the cantilever and the ground plate. The voltage is in the category of hard excitation. The AC frequency is near one eight of the natural frequency of the resonator. Since the electrostatic force acting on the resonator is proportional to the square of the voltage, it leads to superharmonic resonance of fourth order. Besides the electrostatic force, the system experiences damping. The damping force in this work is proportional to the velocity of the resonator, i.e. it is linear damping. Three methods are employed in this investigation. First, the Method of Multiple Scales (MMS), a perturbation method, is used predictions of the resonant regions for weak nonlinearities and small to moderate amplitudes. Second, the Homotopy Analysis Method (HAM), and third, the Reduced Order Model (ROM) method using two modes of vibration are also utilized to investigate the resonance. ROM is solved through numerical integration using Matlab in order to simulate time responses of the structure. All methods are in agreement for moderate nonlinearities and small to moderate amplitudes. This work shows that adequate MMS and HAM provide good predictions of the resonance.

Dynamic Simulation and Control of a Roller Conveyor

Passive roller conveyors are frequently used in material handling applications to transport objects of various sizes and shapes. Passive systems cannot control unit flow, leading to queues and system jams. In this paper we analyze the performance of a gravity-driven roller conveyor with brakes selectively installed on rollers to control package flow in the load lanes of a transportation hub. Dynamics of the rollers and kinematic interaction with boxes on the conveyor were derived and fully modeled in MATLAB to simulate accurate conveyor behavior. Sensitivity analyses were performed to evaluate the effect of friction, box mass, roller inertia, and other factors. Using heuristic data to define boundary conditions (box weight, size, and input frequency), several control cases were evaluated. Performance was defined by buffering efficiency of the conveyor, or how effectively the conveyor “kept pace” with a person moving boxes from the load conveyor onto a waiting truck. Several dynamic control cases were simulated. It was found that the optimal number of installed brakes is 30% of the total rollers on the conveyor. Even rudimentary brake control schemes (applying a simple duty-cycle on/off to roller brakes) had the potential to increase the conveyor buffer efficiency by 10% over baseline, with the potential for much greater benefits from more “intelligent” closed-loop control schemes. The simulation and optimization of the active roller conveyor gave insights into the behavior of their truck loading system and identified several ways to increase loading efficiency.