Skid-steer Loader Research Articles

Assessment of Hydraulic Oil Properties during Operation of a Mini Loader

This study employs a rigorous methodology to assess the condition of the hydraulic oil in a recently introduced mini skid-steer loader. The assessment is conducted through laboratory analysis, which adheres to a range of international standards. The objective is to provide accurate insights into the viscosity, particle count, and characterisation of the oil, along with thermographic data. The friction of oil is evaluated at specific time points: 0, 10, 100, 125, and 150 h of operation. This examination offers a comprehensive insight into the alterations in oil characteristics during a pivotal period when machine components are undergoing initial consolidation and abrasion to attain the factory-defined performance thresholds. The principal aim of this research is to provide valuable insights into the wear of oil and hydraulic system components through an in-depth analysis of a range of variables. Moreover, the investigation aims to ascertain the impact of this factor on the temperature elevation of system components and accessories to formulate enhanced technical guidelines for implementation. The main results indicate the presence of particles in the oil, resulting in a cleanliness code of 23/21/13, which exceeds the permissible threshold of 20/18/15 specified in ISO 11171. In addition, hydraulic oil shows a viscosity instability of more than 10% due to moisture absorption, leading to wear of mechanical components composed of iron, nickel, copper, zinc, and silicon. This deterioration is corroborated by thermographic evaluations, which reveal a considerable temperature increase in components such as cylinders and system accessories.

ИМПОРТОЗАМЕЩЕНИЕ РАБОЧИХ ОРГАНОВ ДЛЯ МУЛЬЧЕРОВ

In the current conditions, there is a multifaceted urgent problem of meeting the growing demand of agriculture for modern and high-quality equipment. Mulchers for tractors, excavators and skid steer loaders are becoming more and more popular as a type of attachment. Carbide cutting elements for the mulcher have a high resource, do not require sharpening, and are not afraid of small stones in the soil. An urgent task in terms of import substitution is the organization of their production at domestic engineering enterprises, which requires information on the materials used for manufacturing. The purpose of the study is to study the details of working bodies for foreign-made mulchers and to identify domestic analogues for the organization of industrial production in the Russian Federation. Hardness of foreign-made mulcher base is 431…710 HRC; cleaner - 221; carbide plate - 1068 ... 1073; carbide crown - 1062 ... 1076, tool holder - 51 HRC. For the production of working bodies of mulchers, Russian analogues of structural materials can be used. The tool holder and base can be made of steel for castings of ordinary grades 40KhL or 35GL GOST 977-88. For the manufacture of a scraper, chromium steel grade 40X or manganese steel grade 35GL is suitable. Parts should be subjected to a heat treatment consisting of quenching and low stress relief tempering. For the manufacture of hard-alloy elements of cutters, it is advisable to use tungsten sintered alloys of grades VK8 or VK10. Hard alloy elements should be soldered with solder grades LNMts 49-9-0.2, MNMts 55-6-4 or MNMts 9-23.5, which provide high strength of steel-hard alloy joints of 350 ... 450 MPa. It is advisable to weld the scraper to the base as follows. First, the root welds are welded with Sv-08G2S solid section welding wire by semi-automatic gas welding. Then the welded joint is surface hardened with Kiswel K-700HT or WELTEK-H565 flux-cored wire by semi-automatic gas welding. This technology provides a weld with a hardness of 54…60 HRC.

Controlling wheel loader motion along a desired trajectory

Problem. Rigid-frame skid steer front loaders are popular material-handling machines widely used in various industries. However, such loaders experience frequent breakdowns due to high dynamic loads; they are often subjected to intensive tyre wear and excessive fuel consumption. Frequently, these issues arise from the improper actions of an operator. Given the labour intensity of the workflow, an operator, regardless of qualification, cannot ensure optimal loader control at an acceptable speed for a long time. In addition, an operator usually works in harsh environments with a high risk of injury, e.g. due to loss of stability. Manual control of loaders also limits the use of these machines in places that are dangerous for humans, for example, during the response to disasters. The solution to these issues is to automate the loader and exclude the operator from the machine work. One of the tasks of loaders automation is to ensure their movement along a given trajectory from the face to the place of unloading the material and back in the opposite direction. Goal. This work aims to increase the productivity and energy efficiency of a rigid-frame skid steer loader by ensuring its following along a given trajectory. Methodology. Based on the kinematics model of the loader, a two-loop control system for motion along a desired trajectory is designed. The control system combines feedforward and feedback loops. The feed-forward control is based on the desired speeds and accelerations. The closed loop is a state controller that uses the loader distance from the desired trajectory at a given time and the course angle as the state variables. Results. According to the simulation results, the proposed two-loop control system ensures the movement of the loader along a desired trajectory with an accuracy of up to 0.3 m. Originality. Further development of the up-to-date control theory was achieved by applying it to a new object, namely a skid steer front loader with a rigid frame. Practical value. The implementation of the proposed control system will increase the productivity of the loader, as well as reduce the number of accidents at construction sites.

Study of residual stress-strain behavior of a load-bearing system of a skid-steer loader under multiple loads according to the ROPS safety standard

Introduction (problem statement and relevance). Ensuring safety of road vehicles is a relevant problem. It is particularly applicable to the road construction machinery. The paper presents an algorithm that allows obtaining the most accurate results of calculations according to the procedure described in GOST R ISO 3471 (ROPS): Earth-moving machinery. Roll-over protective structures. Technical requirements and laboratory tests.The purpose of the study is to investigate the stress-strain behavior (SSB) of a structure of a utility platform taking into account residual stresses, strains and relaxation of the structure under multiple loads according to the roll-over safety requirements for earth-moving machinery.Methodology and research methods. The paper presents a skid-steer loader cabin model created in a fi nite element analysis program to perform the strength calculations. The comparative assessment was performed based on the results of a full-scale experiment carried out on a real structure and of virtual simulations. The research object is a skid-steer loader cabin. The research subject is the design methods for vehicle load-bearing structures and their use taking into account operating conditions.Scientific novelty and results. An algorithm has been created which takes into account residual stresses, strains and relaxation of the structure for further loading and allowing reduction of a displacement calculation error for a utility platform from 84.5 to 4.5%. The internal energy reached under vertical load is 426% higher, while for the longitudinal load case it is 14.6% higher, than for the option not taking into account residual stresses and strains.Practical signifi cance. The proposed algorithm allows considering the requirements of GOST R ISO 3471 regarding prevention of structure readjustment or repair between loadings, which is an actual operating mode.

Development of a novel spoke structure of non-pneumatic tires for skid-steer loaders using finite element analysis

Skid-steer loaders require advanced tires to overcome the challenges in poor construction areas. In this study, a non-pneumatic tire (NPT) is developed using a finite element method (FEM). The spoke structure is a significant component of the NPTs. It is based on the novel X-shaped spoke and is invented by deriving structural equations to model an NPT for a skid-steer loader. The novel NPT model was analyzed via the FEM to estimate its quasi-static performance, such as the vertical stiffness and local stress at the spoke. The FEM implemented a spoke structure model with mechanical properties of the invented material. In addition, geometric parameters such as the number of spoke sections and thickness were varied to study their effects on the vertical stiffness. Furthermore, the relationship between these geometric parameters was derived using a mathematical equation. A vertical stiffness function was applied to manufacture various sizes and configurations of the novel NPT. Moreover, the novel spoke structure was compared with different spokes of NPTs. We found that the proposed NPT had the highest strength. Consequently, the proposed mathematical model can be used for manufacturing a series of novel NPTs for skid-steer loaders in the future.

Storing Peanuts in Grain Bags

HighlightsExisting bag loading equipment may be used to load both in-shell and shelled oil stock peanuts.Grain bags can be loaded at 1.2 t/m of in-shell peanuts and 2.3 t/m of shelled oil stock peanuts.Existing extraction equipment requires modification to unload shelled oil stock peanuts due to poor flow characteristics.Grain bags not suitable for storing in-shell peanuts due to significant moisture migration and quality reduction under typical Georgia conditions.Abstract.Edible grade farmers’ stock peanuts and shelled oil stock peanuts were stored in hermetically sealed silo or grain bags to determine their suitability for short-term storage. The objectives of the study were to evaluate equipment for loading and unloading the grain bags, the capacity of the grain bags, and the changes in quality. In May 2015, approximately 90 Mg of farmers’ stock (in-shell) peanuts from the 2014 crop were unloaded from a commercial warehouse, transported to Dawson, Georgia, and loaded into two 2.7 m diameter grain bags. Similarly, 85 Mg of shelled oil stock peanuts were loaded into two 2.7 m diameter grain bags. Farmers’ stock bags were unloaded after 30 and 60-d storage. A vacuum extractor and a skid steer loader were used due to wet peanuts in the top of the bag. Both oil stock bags were unloaded after 60-d storage. A skid steer loader was used to unload the oil stock bags because shelled oil stock peanuts did not flow adequately to use the conventional bag extraction equipment. Oxygen content in the farmers’ stock peanuts decreased from ambient levels (21%) to an average of 8.6% after 15-d storage. After 20-d storage, the oxygen content in the oil stock had decreased to 14%. A layer of high moisture peanuts due to moisture migration and subsequent condensation in the top of both of the farmers’ stock bags resulted in the peanuts being unsuitable for human consumption and reduced the value from $342/Mg to approximately $125/Mg for oil stock, a 63% reduction in value. No moisture problems were observed in the oil stock bags when they were unloaded. Based on these studies, sealed grain bags would be unsuitable for temporarily storing farmers’ stock peanuts under typical Georgia conditions. Sealed grain bags could possibly be used to store oil stock peanuts for 60 d, but suitable unloading equipment would have to be found or developed. Keywords: Grain bag, Groundnut, Handling, Hermetic, Peanut, Silo bag, Storage.

Electromechanical Transmission of Skid Steer Loader

The article analyzes the power train components of skid steer loaders. The choice of the scheme and the design of the transmission units of the loader with a traction electric drive is substantiated. The results of calculating the traction characteristic of the straight-line movement of the loader taking into account different values of the coefficient of resistance to movement are presented.

Improving the layout of skid steer loader

The article analyzes the layout of the main components and units of a skid steer loader. The effect of placing the heaviest components on the tipping load is estimated. The necessity of increasing the duration of the loader without refueling is substantiated. An option is proposed to improve the layout of the machine to increase its operational performance. A test arrangement made using a 3D-modeling system is given.

Fatal farm injuries to Canadian children

Children on Canadian farms are at high risk for fatal injury. Ongoing surveillance of these deaths is required to affirm recurrent patterns of injury, and to determine whether historical approaches to prevention have resulted in declines in the occurrence of these traumatic events. We analyzed epidemiological patterns and trends in the occurrence of fatal pediatric farm injuries over 23 years. Records of deaths were obtained from the Canadian Agricultural Injury Reporting system. To contrast more recent data with injury patterns described historically, cases were compared between two time periods. An intentional consensus process was used to finalize key patterns and their clinical or social importance. 374 fatal farm injuries to children in Canada were identified over the 23 years of study; 253 in period 1 and 121 in period 2. While machinery and non-machinery causes of death varied between the two study periods, mean annual rates of fatal injury (approximately 4 per 100,000 children) remained similar. Notably emergent types of injury in recent years included those caused by all-terrain vehicles, skid steer loaders, and drownings. Observed declines in the numbers of fatal farm injuries are most likely attributable to analogous declines in the number of registered farms in Canada. Our findings call into question the effectiveness of pediatric farm safety initiatives that primarily focus on education. Second, while CAIR fatality data are maintained, surveillance of hospitalized injuries has been disbanded and the fatality records require updating. Only by doing so will such surveillance findings provide comprehensive information to inform prevention.

Study of geometric effects on nonpneumatic tire spoke structures using finite element method

This research aims to develop a finite element model of nonpneumatic tires (NPTs) with different spoke shapes to study the geometric effects on the NPT for the maximum stiffness and minimum local stress. Four types of spoke structure were classified from reviewed articles and intellectual property. These were based on a few criteria including (1) manufacturability using polyurethane or engineering polymer as the material and (2) simplicity of the shape, the shape with less complexity and simple patterns. The finite element models of NPTs with different four spoke types were created using the same tread, shear band and the overall dimension. The spoke component of each model was created using 2D elements, with the different thickness to give the same mass. The hyperelastic constitutive equations were used to model behavior of NPT tread and spokes. The finite element analysis of vertical stiffness testing was performed on the NPT models using the maximum load required for skid-steer loaders. The analysis results were then compared to give an overview of load capacity of each model along with each advantage/disadvantage. The model with highest vertical stiffness by weight ratio was selected for the optimum number of spoke. Parabolic trends in vertical stiffness and maximum local stress at different spoke numbers were observed. This study found that the upper design limitation of spoke number was 24 spokes. Thus, the optimized number of spokes can be observed and the finite element model can be used to define the optimum geometry for a novel NPT.

Point cloud-based estimation of effective payload volume for earthmoving loaders

Construction and mining require high levels of planning and productivity. Planning and management of operational targets and performance requires taking into account several variables, among which the amount of moved, loaded and unloaded material is one the main ones. This motivates the development of an approach for the estimation of the volume of material transported in field operations by loader trucks. The proposed methodology employs a three-dimensional point cloud representation of the volume and is tested using a skid-steer loader. The volume estimation process involves the segmentation of the loader's bucket from the raw point cloud using machine learning techniques. The segmented point cloud is associated with a pre-constructed reference model of the empty bucket. The volume is computed from a surface model built using the alpha shape algorithm applied to the Delaunay triangulation of the segmented point cloud. Several field experiments were carried out using a stereo camera for five different volumes of material and the bucket at different heights. A 95% accuracy was obtained on average. The encouraging results suggest that effective volume estimation for different bucket types would be possible using the proposed methodology.

$\mathcal {H}_\infty$-Based Terrain Disturbance Rejection for Hydraulically Actuated Mobile Manipulators With a Nonrigid Link

Decoupling the end-effector motion from that of the mobile base of mobile manipulators traversing uneven terrains is important. This is especially so in mining, where material spillage from excavators and front-end loaders reduces productivity and slows down operations because of increased clean-up and maintenance times. Thus, this article proposes a strategy that relies on H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> feedback control combined with feedforward action to improve the rejection of terrain disturbances that affect the orientation of the end-effector. The dynamic model of the mobile manipulator considers a floating base with nonpermanent contacts at each wheel, hydraulic actuators with nonlinear dynamics and a nonrigid arm. The arm flexibility is modeled as a passive spring-damper joint to account for inherent cantilever effects of real excavators and loaders. The analysis considers three different H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> controller structures (single-input single-output (SISO) with feedforward, single-input multiple-output without feedforward, and multiple-input multiple-output without feedforward) to determine the benefits or disadvantages of employing the pitch rate of the mobile base as a feedforward control action or as an input handled by the H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> controller and using only the end-effector actuator or also the other actuated joints of the arm. The root-mean-square error (RMSE) was reduced between 73.8%-86.0% when driving an industrial semiautonomous skid-steer loader over a ramp using the SISO H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> controller with feedforward action.The tilt angle error was kept on average less than 0.9 ± 0.1°. The same controller yields a reduction of the RMSE between 23.5%- 38.4% and a tilt angle error smaller than 3.39 ± 0.07° on average when traversing over a bump. Hence, the strategy proposed to reject ground disturbances should contribute to reducing material spillage of existing autonomous machines that navigate with little operator intervention along mining galleries, but that cannot avoid disturbing material lying on the ground or the characteristic unevenness of mining terrains.

Chassis design of skid steer loaders

The article provide analyzes the design features of the chassis components and assemblies of skid steer loaders. Describes the various options for frame design, engine layout and hydrostatic transmission. A comparison of the wheel and tracked propulsor used on loaders is given.

Online Inertial Parameter Estimation for Robotic Loaders

Payload estimation is essential to measure productivity, evaluate efficiency in industrial operations and adapting control laws according to the carried weight. One particular problem is to identify how much mass is carried in a mining machine while it is being operated without using strain gauge sensors which require frequent calibration and are prone to failure due to mechanical stress. This paper presents an on-line method to estimate a loader’s payload mass, rotational inertia and viscous friction coefficients employing inertial, torque and speed measurements. The proposed approach introduces a mutual information criterion to select those acceleration and velocity measurements that jointly with the excitation force ensure the identifiability of the parameters. The approach relies on the recursive least-squares algorithm for fast update of the parameters. The proposed strategy is also compared to the implementations based on variants of the least-squares estimator, such as the feasible generalized least squares and the total least squares approach. The approach is tested in simulation and validated in experiments with an industrial semi-autonomous skid-steer loader Cat®262C for different loads. Results show that using the recursive least squares it is possible to estimate the parameters with the same level of accuracy than OLS approach, while not needing a large buffer for estimation. Mass is effectively estimated with an RMS error below 1% the total mass of the machine.

Unloading Farmers' Stock Warehouses with a Peanut Vacuum

ABSTRACT A peanut vacuum developed by redesigning an existing grain vacuum (vac) specifically to handle farmers' stock peanuts was tested. The peanut vac consists of a PTO-driven positive displacement blower, two cyclone separators, and a hydraulically-powered airlock valve. The blower pulls air and farmers' stock peanuts through a length of suction hose into the first cyclone separator where the peanuts are separated from the airstream. The air then travels to a second cyclone separator where the suspended dirt and other fine particles are separated from the airstream. The cleaned air proceeds through the blower and is blown through a discharge chute beneath the outlet of an airlock valve mounted on the bottom of the first cyclone. Farmers' stock peanuts from the first cyclone fall from the outlet of the airlock valve into the airstream in the discharge chute and are conveyed up into a waiting trailer. The peanut vac is powered by a 1000-rpm PTO shaft of a tractor supplying a minimum of 75 kW. Initial feasibility tests were conducted while unloading 1/10-scale farmers' stock warehouses to determine the optimum operating parameters to minimize mechanical damage. The optimized peanut vac was taken to two locations in South Georgia and used to extract peanuts from farmers' stock warehouses in addition to the conventional equipment used for warehouse bailout. The weight of peanuts on each truck, time to fill each truck, and the farmers' stock grade factors for the peanuts in each truck was recorded and compared by conveyance method. At the first location, the conventional equipment consisted of a skid-steer loader with an oversized bucket driven into the pile of peanuts. The peanuts were emptied into a surge bin feeding a portable conveyor belt that conveyed the peanuts into a waiting truck. At the second location, a large articulated bucket loader was used in lieu of the skid-steer loader. Peanuts loaded using the conventional method averaged 5.2% foreign material (FM) and 6.7% loose shelled kernels (LSK). Peanuts loaded using the peanut vac averaged 2.7 and 4.9% FM and LSK, respectively. Trucks were loaded at a rate of 187 MT/h using conventional equipment compared to 61MT/h using the peanut vac.

Methods of Collecting and Analyzing Rearward Visibility Data for Agricultural Machinery: Hazard and/or Object Detectability.

Recent interest in rearward visibility for private, construction, and commercial vehicles and documentation of rearward runovers involving bystanders outside the field of vision of the vehicle operator led to an investigation into the need for enhanced methods of rearward visibility for large, off-highway, agricultural equipment. A review of the literature found limited relevant research and minimal data on incidents involving rearward runovers of bystanders and co-workers. This article reviews the findings regarding the methods identified and tested to collect and analyze rearward visibility data, from the operator's perspective, for large self-propelled agricultural equipment, including the four-wheel drive tractors, combines, agricultural sprayers, and skid-steer loaders that are increasingly found on agricultural production sites. The methods identified, largely drawn from research conducted on private and commercial vehicles, were tested to determine their application in identifying rearward blind spots. These methods are described, and the findings from field-testing of specific machines are provided. Recommendations include establishing an appropriate engineering standard regarding rearward visibility of agricultural equipment with limited rearward vision and the use of rearward alarm systems for warning bystanders of rearward movement.

General Dynamic Model for Skid-Steer Mobile Manipulators With Wheel–Ground Interactions

The design of motion controllers that could reduce terrain disturbances propagated to the arm and optimize the trajectories of skid-steer mobile manipulators (SSMMs) working in agricultural, construction, or mining environments requires accurate physical models capable of correctly representing disturbances caused by changes in terrain slope, loss of traction, and other wheel-ground interactions. Therefore, this paper develops the forward dynamics equations of motion and proposes a general model for SSMMs. The novelty of the model is that it considers a floating-base with nonpermanent wheel-ground contacts, i.e., the mobile base has 6-degree of freedom (DOF) and the wheels may lose contact with the terrain. Unlike the existing models, the proposed one is general because the procedure can be extended to MMs with an arbitrary number of arms or wheels and does not restrict the mobile base to planar 2-D motions. Furthermore, it takes into account the loss of traction and the deformation of the wheel–ground contacts. The experimental results involving a small SSMM with a 3-DOF arm and an industrial skid-steer loader validate the physical fidelity of the model. Although the focus of this paper is not in control aspects, one of the examples shows the role physically accurate models can have in the design of end-effector motion controllers, and its potential application to the design of controllers capable of decoupling the arm motion from ground disturbances.

Determining the Effectiveness of Mirrors and Camera Systems in Monitoring the Rearward Visibility of Self-Propelled Agricultural Machinery.

This study concerned the ability of operators of tractors and other self-propelled agricultural machinery to visually recognize objects and/or hazards within close proximity to the rear of those machines and/or any implements in tow, especially when backing up. It was hypothesized that the data collected would identify the factors affecting rearward visibility and help determine the effectiveness of two backup-assisting devices (i.e., mirrors and camera systems) in enhancing the operator's ability to observe objects or hazards. The study's experimental design involved the following: (1) selecting nine self-propelled machines for testing (five tractors of varying sizes, a combine, a sprayer, a skid steer loader, and a UTV); (2) laying out a five cell by five cell test grid behind each machine, with an indicator pole centered in each cell; (3) positioning the mirrors (exterior/interior) and camera system (camera and display monitor) for maximum visibility; and (4) collecting images from a 50th percentile male operator's eye midpoint position. The findings were recorded graphically onto a master grid for the backup-assisting devices (both individually and in combination) on each machine. Analysis of the results confirmed that various issues related to the machines impact the effectiveness of mirrors and camera systems in enhancing rearward visibility. Among them are the operator station's design and configuration, seat adjustability, optional accessories, exterior lighting, type of implement in tow, hitching method, and highway transport mode. These findings led to recommendations relative to each of the mirrors and camera systems, as well as observations of operator interactions with accessories and perceived effects on the operator's ability to view obstructed areas in close proximity to the machinery.

Optimal Power Management of Hydraulic Hybrid Mobile Machines—Part I: Theoretical Studies, Modeling and Simulation

Recent demands on improved system efficiency and reduced system emissions have driven improvements in hydraulic system architectures as well as system supervisory control strategies employed in mobile multi-actuator machinery. Valve-controlled (VC) architectures have been in use for several decades and have seen moderate improvements in terms of system efficiency. Further, throttle-less concepts such as displacement-controlled (DC) actuation have been recently proposed and successfully demonstrated efficiency improvements in numerous prototypes (wheel-loaders, excavators, and skid-steer loaders) of different sizes. The combination of electric or hydraulic hybrid systems for energy recovery (for a single actuator) with VC actuation for the rest of the actuators has also been recently deployed by original equipment manufacturers (OEMs) on some excavator models. The combination of DC actuation together with a series hydraulic hybrid actuator for the swing drive has been previously proposed and implemented as part of this work, on a mini-excavator. This combination of highly efficient DC actuation with hydraulic hybrid configuration allows drastic engine downsizing and efficiency improvements of more than 50% compared to modern-day VC-actuated systems. With a conservative, suboptimal supervisory control, it was previously demonstrated that over 50% energy savings with a 50% downsized engine over the standard load-sensing (LS) architecture for a 5-t excavator application. The problem of achieving maximum system efficiency through near-optimal supervisory control (or system power management) is a theoretically challenging problem, and has been tackled for the first time in this work for DC hydraulic hybrid machines, through a two-part publication. In Part I, the theoretical aspects of this problem are outlined, supported by simulations of the theoretically optimal supervisory control as well as an implementable, near-optimal rule-based supervisory control strategy that included a detailed system model of the DC hybrid hydraulic excavator. In Part II, the world's first prototype DC hydraulic hybrid excavator is detailed, together with machine implementation of the novel supervisory control strategy proposed in Part I. The main contributions of Part I are summarized below. Dynamic programming (DP) was employed to solve the optimal supervisory problem, and benchmark implementable strategies. Importantly, the patterns in optimal state trajectories and control histories obtained from DP were analyzed and identified for different working cycles, and a common pattern was found for engine speed and DC unit displacements across different working cycles. A rule-based strategy was employed to achieve near-optimal system efficiency, with the design of the strategy guided by optimal patterns. It was found that the strategy replicates optimal system behavior with the same rule for controlling engine speed for different cycles, but different rules for the primary unit (of the series-hybrid swing drive) for different cycles. Thus, in terms of practical implementation of a rule-based approach, the operator is to be provided with a family of controllers from which one can be chosen so as to have near-optimal system behavior under all kinds of cyclical operation.

Analysis of Skid Steer Loader Steering Characteristic

In order to analyze the steering dynamic characteristic of the skid steer loader, a cosimulation model of steering system based on theoretical analysis of skid steer loader steering process was established by using AMESim software platform and Motion software platform. The dynamic characteristics of unilateral, bilateral steering conditions and the load characteristics of steering process were analyzed through simulation and verified by experiment. The comparison of dynamic model and experimental results shows that the error between simulation data and experimental data is within 10%, and the model can be used in system matching and performance prediction.