Wave-based control of vibration in an active suspension system with a quarter-car model

Wave-based control (WBC) offers a relatively novel approach to the challenge of controlling flexible systems by treating theinteraction between the actuator and the system as the launch and absorption of mechanical "waves" or propagating disturbances.This control technique has been often used for the systems with lumped models where the entire system mass is allocated todiscrete lumped rigid masses which are linked together via flexible massless springs [1-3].WBC, known for its model-independent nature, is a robust approach but unexplored in active suspension systems to date. Thisstudy adapts WBC to a lumped mass-spring quarter-car suspension model. Applying a nonlinear model for an electro-hydraulicservo actuator and quarter suspension system, the 'force impedance' version of WBC [2], shown in Figure 1, is adapted, andemployed for its effective vibration control.In road vehicles, active suspension systems utilize actuators to generate adjustable forces between the vehicle's sprung andunsprung masses, enhancing both ride comfort and handling. Ride comfort pertains to the vehicle's ability to reduce mechanicalvibrations felt by passengers, caused by uneven road surfaces [4]. These suspension systems incorporate actuators that modulateforces between the sprung and unsprung masses, playing a pivotal role in improving ride comfort in future vehicle designs.The performance of different controllers in active suspension systems have been extensively researched but this work exploresthe effectiveness of wave-based controller on dampening vibrations of these systems which has not been studied to date.<br/

Gantry crane control of a double-pendulum, distributed-mass load, using mechanical wave concepts

© Author(s) 2013. This work is distributed under the Creative Commons Attribution 3.0 License.The overhead trolley of a gantry crane can be moved in two directions in the plane. The trolley is attempting to control the motion of a suspended, rigid-body, distributed mass load, supported by a hook, modelled as a lumped mass, in turn connected to the trolley by a light flexible cable. This flexible system has six degrees of freedom, four variables describing the flexible, hanging load dynamics and two (directly controlled) input variables for the trolley position. The equations of motion are developed and the crane model is verified. Then a form of wave-based control (WBC) is applied to determine what trolley motion should be used to achieve a reference motion of the load, with minimum swing during complex manoeuvres. Despite the trolley's limited control authority over the complex, flexible 3-D dynamics, WBC enables the trolley to achieve very good motion control of the load, in a simple, robust and rapid way, using little sensor information, with all measurements taken at or close to the trolley

Wave-based control of under-actuated flexible structures with strong external disturbing forces

Wave-based control of under-actuated, flexible systems has many advantages over other methods. It considers actuator motion as launching a mechanical wave into the flexible system which it absorbs on its return to the actuator. The launching and absorbing proceed simultaneously. This simple, intuitive idea leads to robust, generic, highly efficient, precise, adaptable controllers, allowing rapid and almost vibrationless re-positioning of the system, using only sensors collocated at the actuator-system interface. It has been very successfully applied to simple systems such as mass-spring strings, systems of Euler-Bernoulli beams, planar mass-spring arrays, and flexible three-dimensional space structures undergoing slewing motion. In common with most other approaches, this work also assumed that, during a change of position, the forces from the environment were negligible in comparison with internal forces and torques. This assumption is not always valid. Strong external forces considerably complicate the flexible control problem, especially when unknown, unexpected or unmodelled. The current work extends the wave-based strategy to systems experiencing significant external disturbing forces, whether enduring or transient. The work also provides further robustness to sensor errors. The strategy has the controller learn about the disturbances and compensate for them, yet without needing new sensors, measurements or models beyond those of standard wave-based control

Optimal Witnessing of Healthcare IoT Data Using Blockchain Logging Contract

Verification of data generated by wearable sensors is increasingly becoming of concern to health service providers and insurance companies. There is a need for a verification framework that various authorities can request a verification service for the local network data of a target IoT device. In this paper, we leverage blockchain as a distributed platform to realize an on-demand verification scheme. This allows authorities to automatically transact with connected devices for witnessing services. A public request is made for witness statements on the data of a target IoT that is transmitted on its local network, and subsequently, devices (in close vicinity of the target IoT) offer witnessing service. Our contributions are threefold: (1) We develop a system architecture based on blockchain and smart contract that enables authorities to dynamically avail a verification service for data of a subject device from a distributed set of witnesses which are willing to provide (in a privacy-preserving manner) their local wireless measurement in exchange of monetary return; (2) We then develop a method to optimally select witnesses in such a way that the verification error is minimized subject to monetary cost constraints; (3) Lastly, we evaluate the efficacy of our scheme using real Wi-Fi session traces collected from a five-storeyed building with more than thirty access points, representative of a hospital. According to the current pricing schedule of the Ethereum public blockchain, our scheme enables healthcare authorities to verify data transmitted from a typical wearable device with the verification error of the order 0.01% at cost of less than two dollars for one-hour witnessing service.Comment: 12 pages, 12 figure