In this paper, a cleaning robot is designed to remove the marine fouling attached to a marine steel pile. In the following study, in order to analyse the process of cleaning marine fouling attached to a rough substrate, the barnacle is taken as a typical case in order to study the horizontal cutting force in the scarping process for removing barnacles on a rough substrate. The adhesion model of the barnacle was established on a rough rigid substrate. Considering both right angle cutting theory and the Peel Zone method, a scraping means and horizontal cutting force model for rough surface cleaning are proposed for the study of the surface cleaning of steel piles. In order to make the model more accurate, the finite element method is used to analyze and compare its errors. Through comparative analysis, it is known that the relative average errors about the cutting force in the horizontal direction are less than 15%. The analysis shows that the blade rake angle and rough substrate have a great influence on the horizontal cutting force. It can be concluded that the cutting force needed to clean the barnacle attached to the surface decreases correspondingly as the rake angle of the blade increases; and the rougher the substrate is, the greater the horizontal cutting force required. It is recommended to use 60° for blade rake angle. We can use the model to predict the horizontal cutting force and blade rake angle in the design of a cleaning robot.

This paper proposes an orthogonal experimental design based on the optimization method for the nozzle geometry of an underwater abrasive water jet, with the objective of maximizing the cutting capacity and minimizing the nozzle-erosion rate. Parameter effects on the nozzle’s cutting capability and life are analyzed. This analysis shows that while the contraction-section curve, the contraction-section axial length and the focus-section axial length mainly affected the service life of the nozzle, the nozzle-outlet diameter mainly affected the cutting capacity of the nozzle. The effect significances of the structural parameters, from high to low, are outlet diameter > axial length of contraction section > axial length of focusing section > contraction curve. According to the optimal performance index for this nozzle, the optimal nozzle structure parameters were a contraction-section curve of $A_4$ (parabolic), an axial length of contraction section of 20 mm, an outlet diameter of 2 mm, and an axial length focusing section of 10 mm. With the optimal parameters, the nozzle performance excellence index was $Q$ = 1.441, which is the optimization objective and 44.1% higher than the baseline of the conical nozzle; the maximum velocity at a distance of 100 mm was improved by 56% and the maximum erosion rate was reduced by 72% compared to that of the conical nozzle.

A grasp planning method based on the volume and flattening of a generalized force ellipsoid is proposed to improve the grasping ability of a dexterous robotic hand. First, according to the general solution of joint torques for a dexterous robotic hand, a grasping indicator for the dexterous hand—the maximum volume of a generalized external force ellipsoid and the minimum volume of a generalized contact internal force ellipsoid during accepted flattening—is proposed. Second, an optimal grasp planning method based on a task is established using the grasping indicator as an objective function. Finally, a simulation analysis and grasping experiment are performed. Results show that when the grasping experiment is conducted with the grasping configuration and positions of contact points optimized using the proposed grasping indicator, the root-mean-square values of the joint torques and contact internal forces of the dexterous hand are at a minimum. The effectiveness of the proposed grasping planning method is thus demonstrated.

Radial seals are sensitive to axial overload failure and may cause leaks. This paper presents two semi-analytical methods for the joint strength and sealing performance of the subsea pipeline compression connector under axial overload failure. The method for the joint strength consists of two parts: One is the analytical model for the joint strength of the connection and seal under axial tension and compression conditions. The models are based on membrane theory, considering the hardening and bending effects. The other is a two-dimensional, axisymmetric finite element model for the joint strength of the radial metal seal. The semi-analytical method for the overload sealing performance is derived using a finite element model and the Reynolds equation of the laminar flow. The effects of critical parameters on the joint strength and the overload sealing performance are analyzed. The experiments are carried out with specimens and prototypes to evaluate the evolution of the sealing interface and the joint strength. The results show that both the internally turned sealing surface and the deflection of the pipe can improve the joint strength. In addition, the compression-type connector can remain sealed under the maximum axial overload. The proposed methods allow the prediction and identification of the overload joint strength and the sealing condition of the compression-type connector and provide a better understanding of the radial metal seal under the axial overload condition.

A new algorithm is proposed for the optimization of grasping torques. Previous work revealed that the optimization of the contact force can be simplified as a linear programming problem by replacing the nonlinear friction cone with a polyhedral cone. On this basis, further simplification and linearization is completed for various grasp contact constraints of the grasping system, and an optimization model is established with the minimum sum‐of‐squares of joint torques as an objective function. A timely and effective algorithm based on key constraint sets is then established. This methodology optimizes the joint torque directly and facilitates the control of the dexterous hand. A numerical example and experimental results show that the optimization algorithm has high precision and good real‐time performance. The joint torque output obtained using the proposed algorithm was 27.6% lower than the result of the previous algorithm. The optimization algorithm can thus be used for optimal grasping control of a dexterous hand.