A self-propelled machine for combined potato harvesting and residual plastic film retrieval is presented in this paper. The machine was designed collaboratively and built at the College of Mechano-Electronic Engineering of Gansu Agricultural University. It is intended for slow slope and horizontal terraces in hilly and mountainous areas of Northwest China, where regular-size harvesters cannot operate. The machine can realize the combined operations of potato digging, potato separation from soil and plastic film, potato collection and bagging, and residual plastic film retrieval. Through engineering analyses, the main systems of the machine were calculated, and their operating parameters were estimated. These include the digging and lifting device, the potato–plastic-film separation device, and the residual plastic film retrieval device. Field tests were performed at a 0.5 m/s driving speed of the machine, while the linear speed of the lifting chain of the digging and lifting device was 1.5 m/s, the tilting angle of the conveying chain of the potato and plastic film separation device was 50°, its linear speed was 0.6 m/s, and the linear speed of the lifting screen of the circulating lifting device was 0.7 m/s. With these settings, the average productivity of the machine was 0.12 ha/h. The loss rate, damage rate, and potato bruising rate were 1.8%, 1.4%, and 2.8%, respectively; the potato impurity rate was 3.6%; and the residual plastic film retrieval rate was 83%—all above industry standards. This research provides a solution to the problem of mechanized potato harvesting and plastic mulch retrieval on small, slopped plots of land in Northwest China and in other parts of the world where similar conditions exist.

The paper presents a general approach to the steady-state efficiency analysis of one degree of freedom (1-DOF) speed increasers with one or two inputs, and one or two outputs, applicable to wind, hydro and marine-current power generating systems. The mechanical power flow, and the efficiency of this type of complex speed increasers, are important issues in the design and development of new power-generating systems. It is revealed that speed increases, with in-parallel transmission of the mechanical power from the wind or water rotors to the electric generator, have better efficiency than serial transmissions, but their efficiency calculus is still a challenging problem, solved in the paper by applying the decomposition method of complex speed increasers into simpler component planetary gear sets. Therefore, kinematic, steady-state torque and efficiency equations are derived for a generic 1-DOF speed increasers with two inputs and two outputs, obtained by connecting in parallel two gear mechanisms. These equations allow any speed increaser to be analysed with two inputs and one output, with one input and two outputs, and with one input and one output. We discuss a novel design of a patent-pending planetary-gear speed increaser, equipped with a two-way clutch, which can operate (in combination with the pitch adjustment of the rotors blades) in four distinct configurations. It was found that the mechanical efficiency of this speed increaser in the steady-state regime is influenced by the interior kinematic ratios, the input-torque ratio and by the meshing efficiency of its individual gear pairs. The efficiency of counter-rotating dual-rotor systems was found to be the highest, followed by systems with counter-rotating electric generator, and both have higher efficiency than conventional systems with one rotor and one electric generator with fixed-stator.

To improve soil clod removal and reduce potato damage in potato combine harvesters, this study investigates the processes involved in soil clod removal and potato collisions within the bar-lift chain separation device of the harvester. It outlines the structure and working principles of the machine, theoretically analyzes the key dimensions of the digging device and potato–soil separation components, and derives specific structural parameters. A dynamic mathematical model of the bar-lift chain is established, from which the dynamic equations are formulated. The analysis identifies factors that influence the dynamic characteristics of the bar-lift chain. This study examines the working principles and separation performance of the potato–soil separation device, with a focus on the collision characteristics between potatoes and both the screen surface and the bars. Key factors such as the separation screen’s line speed, the harvester’s forward speed, and the tilt angle of the separation screen are considered. Simulations are performed using a coupling method based on the Discrete Element Method (DEM) and Multi-Body Dynamics (MBD). Through simulation experiments, the optimal parameter combinations for the potato–soil separation device are determined. The optimal working parameters are identified as a separation screen line speed of 1.25 m/s, a forward speed of 0.83 m/s, and a tilt angle of 25°. Field harvesting experiments indicate a potato loss rate of 1.8%, a damage rate of 1.2%, an impurity rate of 1.9%, a skin breakage rate of 2.1%, and a yield of 0.15–0.21 ha/h. All results meet national and industry standards. The findings of this research provide valuable theoretical references for simulating potato–soil separation in combine harvesters and optimizing the parameters of these devices. Future potential research will consider the automatic regulation of the excavation volume of the potato–soil mixture, aiming to achieve intelligent control of the potato–soil separation operation.

This paper presents a unified approach to the problem of dimensional synthesis of the five-link, four-link, and three-link (double-wishbone) suspension mechanisms with a rack-and-pinion steering input. In a simplified approach, the guiding links are assumed to be removed from their joints, allowing the wheel to be exactly driven through a number of prescribed jounce–rebound and steering positions during the kinematic synthesis process. Alternatively, the tie rod is maintained in place, and the rack length and the lengths of the remaining four guiding links are allowed to vary. An optimization problem based on the aggregated change in distance between the released ball joints evaluated in the aforementioned positions is then defined. By prescribing to the wheel a jounce–rebound motion only, rear-suspension mechanisms of the five-link, four-link, and three-link types can be conveniently synthesized by following the same procedure. Several solutions obtained through synthesis are then analyzed for their changes in steering error, recessional wheel motion, wheel track, toe angle and camber angle, showing very promising results. Additionally, a comprehensive review of nearly 150 publications relevant to the suspension design of automobiles is provided in the paper.

The seed metering process of a fluted force-feed seeder was simulated using the Discrete Element Method and its parameters optimized using the Box–Behnken Design of Experiments and the Response Surface Method. The rotational speed of the feed roller, the lead (helix) angle of the flutes, and the number of flutes were the independent variables, while the response value was the seeding uniformity index. Two regression models were investigated, and the following conclusions drawn. For the flute lead angle between 0 and 10 degrees, and the number of flutes between 10 and 14, it was found that the number of flutes and the lead angle influenced the seeding performance the most, with the order of importance being the (i) number of flutes, (ii) lead angle and (iii) roller speed. For the flute lead angle between 5 and 15 degrees, and the number of flutes between 12 and 16, it was found that the roller speed and the number of flutes influenced the seeding performance the most, with the order of importance being the (i) roller speed, (ii) number of flutes and (iii) flute lead angle. The two regression models were then minimized for the seeding uniformity index and the corresponding optima verified experimentally on a conveyor belt test stand fitted with an image recognition system.