International Journal of Advanced Design and Manufacturing Technology
Volume:17 Issue: 3, Sep 2024

In machining processes, the self-excited vibration between the cutting tool and the workpiece is an important issue that can result in undesirable effects, for example, poor quality of the final surface, low dimensional accuracy, breakage of the tool, and excessive noise. To anticipate this problem, statistical features of the vibration signal, such as mean, variance, and standard deviation, have been extracted from online measurements. The synthesis criterion (SC), which is based on the standard deviation (STD) and the one-step autocorrelation function (OSAF), has been employed to detect quickly the threshold of chatter vibration. In this article, flexible workpieces with varying cutting depths have been selected to detect online chatter vibrations during milling operations. In order to collect an analog vibration signal, an STM32 card has been selected with a sampling rate up to 20 kSPS. A high-bandwidth, lightweight film piezoelectric sensor is attached to the workpiece. Unlike other sensors, such as load cells or acceleration sensors, the film piezoelectric sensors do not alter the dynamics of the system. In this research, cost-effective hardware is also developed to capture vibration signals reliably and efficiently. The experimental results confirm that the developed SC algorithm can efficiently predict the onset of chatter vibration as it was able to detect the onset of chatter vibrations within 0.18 sec. Thus, the SC algorithm can considerably enhance the milling operations of flexible parts.

Trajectory planning in cable-driven robots is more challenging than rigid-link ones. To maintain the robot control, the cable tensions must be positive during motion. This paper presents a direct collocation approach to solve the optimal trajectory planning based on the minimization of a robot's tension and tension-rate objective functions. Besides, during robot motion, the cables must be tensile. The configuration of a cable parallel robot composed of a 3-cable and a prismatic actuator neutralizes the moving platform’s weight while improving tensionability. To generate smooth trajectories, the proposed method is compared with two standard approaches: GPOPS-II software package which uses Legendre-Gauss-Radu quadrature orthogonal collocation polynomials and direct collocation by using B-spline interpolation curves. Despite the efficiency of using B-spline functions in trajectory planning, numerical simulations demonstrate that the Hermite-Simpson direct collocation approach has a substantial benefit in the computation cost and accuracy for trajectory planning of a cable-driven parallel robot. Also, by choosing appropriate constraints and cost functions, the cable forces in the parallel robot can be well managed.

Industrial heaters play a pivotal role in various processes in industries and consume significant energy resources. Increasing the energy efficiency of these heaters is of great importance in the current energy-saving scenario. This study improves existing heaters by introducing an additional convective section, using the power of computational fluid dynamics to optimize heat transfer and improve overall efficiency. This paper presents a comprehensive study on upgrading existing heaters by incorporating an additional convection section, facilitated by a thermal and computational study. The main focus is on increasing the efficiency of conventional heaters by optimizing the heat transfer process through the newly added convection section. This paper describes the methodology used to analyze, model, and simulate the reinforced system, presents the results generated by CFD, and discusses the implications of the findings on the overall efficiency of the heaters. In this regard, to study and design the optimal mode of energy saving and complying with the conditions of optimal operational performance, various plans are examined and the best method is selected for heater optimization.

Sports equipment is widely available in the international market. The market's focus is on the design of sports equipment to prevent injury, and all equipment must be designed to enable performance without causing injury. The purpose of this study is to design and manufacture a new volleyball and comparison of kinetic components with other volleyballs. The present study is applied and developmental type. We used four full-size Federation International Volleyball (FIVB), official volleyballs (V200W MIKASA made in Japan, FOX volleyball, model Spain, made in the United States, BETA, and new volleyballs made in Iran) to determine the biomechanical components, such as stiffness and Ground Reaction Force (GRF) on that ball. Ground reaction force variables and stiffness of all samples were recorded by a force plate device (sampling rate: 1000 Hz) and Shore C (Newton’s per meter N/m), respectively. There was a significant difference in all groups between stiffness (P<0.001), vertical ground reaction force (vGRF) (P<0.001), and impulse (P=0.012), also the LSD Post Hoc test showed that stiffness, vGRF, and impulse in new volleyball and MIKASA volleyball were less than BETA and FOX volleyballs. The results indicate that the biomechanical components of the new volleyball with MIKASA were similar. Therefore, the new volleyball design appears to be suitable for an official competition. Nonetheless, more clinical studies are needed to evaluate the kinetic and kinematic parameters of using new volleyball.

The Reinforcement Learning Approach (RL) is used to solve the path-planning problem of an autonomous mobile robot in unknown environments. Despite that RL is a recent and powerful tool, it requires a lot of training processes because there are so many parameters in the agent’s training process. Some of these parameters have a larger effect on the convergence of the learning process than others, so, knowing these parameters and their suitable values makes the training process more efficient, saves time, and consequently makes the trained agent execute the required task successfully. No analytical equations are available to determine the best values for these parameters, therefore, in this paper, a statistical analysis is made using the design and analysis of experiment (DoE) methods to determine the parameters that have the largest effect on the training process. After that, analysis is done to determine the values of the most effective parameters. Results show that the determined parameters lead to a successful autonomous path planning in different unknown environments

In critical manoeuvres where the maximum tire-road friction capacity is used, the vehicle's dynamic behaviour is highly nonlinear, and there are strong couplings between longitudinal and lateral dynamics. If the tire-road friction conditions change suddenly during these manoeuvres, the vehicle control will be very complicated. The innovation of this research is a control algorithm to manage vehicles on a curved path with sudden tire-road friction change. The main advantage of the proposed controller is that it is robust to the change of the friction coefficient and other unmodeled uncertainties and ensures vehicle stability with low computational volume. The evaluation of the proposed adaptive controller has been done using the full vehicle model in CarSim software and by defining three different manoeuvres, moving at a constant speed on a curved road, lane-change, and lane-change with braking. Also, in the obtained results, the noise of the yaw speed signals and longitudinal and lateral accelerations are considered. The estimation of the longitudinal and lateral velocities is also done using these data. The obtained results showed that the proposed integrated control can manage the highly nonlinear dynamics of the vehicle in the existence of a sudden and significant change in the friction coefficient.