Heave compensation systems are essential for operations’ safety, reliability, and efficiency in harsh offshore environments. This paper investigates the vibration suppression problem of a type deep-sea robot with length time variation operating environments active heave systems, where hydraulic compensators implement actuators input nonlinearity, model coupling, unknown nonlinear disturbances. ...

Heave compensator is a system that mitigates transmission of heave movement from vessels to the equipment in the vessel. In drilling industry, a heave compensator enables drilling in offshore environments. Heave compensator attenuates movement transmitted from the vessel to the drill string and drill bit ensuring security and efficiency of the offshore drilling process. Common types of heave co...

Frost heave, which is the volumetric expansion of frozen soil, has great ecological significance, since it creates water storage spaces in soils at the beginning of the growing season in cold temperate forests. To understand the characteristics of frost heave in seasonally frozen soil and the factors that impact its extent, we investigated the frost heave rates of forest soil from different dep...

Abstract. A heave compensation system is one of the absolutely necessary instruments to secure mining operation. The heave compensation system includes a heave compensated platform which is to compensate heave motion and a gimbaled platform which is to accommodate pitch and roll. The simulation of a nonlinear model based on fuzzy PID control is performed. The results show that the compensation ...

Wave energy converters (WECs) often include a submerged heave reaction plate located at a depth where the surrounding water is minimally disturbed by the passing surface waves. Heave plates provide a relatively stationary and artificially massive body to which WECs transfer the reactionary forces generated as their power-takeoffs (PTOs) resist the motion induced by the incoming waves. To date l...

We develop a mathematical model of frost heave in colloidal soils. The theory accounts for heave and consolidation, while not requiring a frozen fringe assumption. Two solidification regimes occur: a compaction regime in which the soil consolidates to accommodate the ice lenses, and a heave regime during which liquid is sucked into the consolidated soil from an external reservoir, and the added...

Severe environment in deep ocean affects operating reliability and security of coring drill. Adopting heave motion signal measured by accelerometer to confirm heave compensation of coring drill, the compensation control method is proposed using disturbance observer to restrain the disturbance. Then, the disturbance observer is designed. The heave motion simulation for coring drill is done with ...

This paper presents a constrained finite horizon model predictive control (MPC) scheme for regulation of the annular pressure in a well during managed pressure drilling from a floating vessel subject to heave motion. In addition the robustness of a controller to deal with heave disturbances despite uncertainties in the friction factor and bulk modulus is investigated. The stochastic model descr...

A generalized model for secondary frost heave is developed based on the one-dimensional model of O'Neill and Miller. Secondary frost heave arises during freezing owing to cryostatic suction effects that can increase the upward water permeation to facilitate ice-lens growth and increased heave. Nondimensionalization and scaling are used to simplify the model equations and to identify a dimension...

To elucidate the early stages of heave, settlement and fracture of intact frost-susceptible rock by temperature cycling above and below 0°C, two physical modelling experiments were performed on 10 rectangular blocks 450 mm high of fine-grained, soft limestone. One experiment simulated 21 cycles of bidirectional freezing (upward and downward) of an active layer above permafrost, and the other si...