This paper describes the development and test of a novel LiDAR based combine harvester steering system using a harvest scenario and sensor point cloud simulation together with an established simulation toolchain for embedded software development. For a realistic sensor behavior simulation, considering the harvesting environment and the sensor mounting position, a phenomenological approach was chosen to build a multilayer LiDAR model at system level in Gazebo and ROS. A software-in-the-loop simulation of the mechatronic steering system was assembled by interfacing the commercial AppBase framework for point cloud processing and feature detection algorithms together with a machine model and control functions implemented in MATLAB/ Simulink. A test of ECUs in a hardware-in-the-loop simulation and as well as HMI elements in a driver-in-the-loop simulation was achieved by using CAN hardware interfaces and a CANoe based restbus simulation.
Powertrains for mobile applications need to fulfil various requirements regarding functionality, efficiency, and emissions. Mechanical and hydraulic drive components are still the most used drive technologies in mobile applications, due to their power density. Despite the known drawbacks in this regard, electric drives are used in various machines (e.g. forklifts, dumpers) to take advantage of such benefits as low maintenance costs, local emissions, and good controllability [1]. Current disadvantages, such as power density and component costs are weakening, due to intensive development work on electric drives. As a result, another drive technology has to be taken into account when developing mobile machines. This leads to an increasing complexity for developers and to the question addressed in this article, if and how an adapted development method can support future development work. Developments in mobile applications are moving towards electrically driven machines to reduce emissions. However, until now electrical components have rarely found their way into mobile applications, often due to their lower power density compared to hydraulic actuators. Some of these disadvantages can be accepted to reduce maintenance effort or reduce local emissions with electric drives. The disadvantage of higher component costs is expected to diminish, due to current developments in the automotive industry. However, the hydraulic technology is often the only possible solution for some applications (e.g. translational movements), and the supposed low efficiency of hydraulic drives has been put into question in various studies [2, 3]. Continuous variable transmission (CVT) concepts show that the biggest benefit can be achieved by combining different drive technologies to use technology based benefits. Neither electric, hydraulic nor mechanical actuation can be neglected in future development processes. Each technology has its benefits to improve current drive concepts. The big challenge is to manage the increasing complexity.
Today's demands for both, low fuel consumption and low vehicle emissions, requires innovative drivetrain concepts. In the field of transmissions, the development of new transmissions is assisted by computer based synthesis. Thus, many mathematically described possible solutions (transmission topologies) can be found. Transmission topology to be constructed nowadays is selected by a designer primarily on the basis of topology's calculated transmission steps, ratio range, planet wheel rotational speed as well as state and load of shift elements. The prediction of topology's future characteristic design values regarding to required packaging space, weight and losses are not reliable before the topology has been worked out as design concept. Manually constructed design concepts by a designer is time-consuming and work-intensive which limits the amount of constructional designed topologies and leads to only few comparable constructional designed topologies on the comparison level of design concepts (required packaging space, weight and losses). Automated design concept generation whereas increases topology's evaluation level by the objectively calculated criteria. Additionally, automated generated design concepts can be used as basis for followed up detail construction and reduces design effort.
The design problem of hybrid electric drivetrains has a large design space, especially, when complex dedicated hybrid transmissions that combine an internal combustion engine with multiple electric machines are considered. To evaluate a drivetrain design over a driving cycle, a transmission model is needed. To avoid the need of modeling every drivetrain concept individually, a generic transmission model for hybrid electric drives is developed. The developed model integrates the dynamic behavior of all conventional-, electric-, and hybrid- transmission mode types. Mode types and mode type dependent control variables are defined. The outputs of the model are the torque and rotational speed of all power sources of the drivetrain. The inputs of the model are the torque and speed of the wheels, and the control variables. As a practical example, the model is used to compare the energy efficiency of two complex dedicated hybrid transmissions by optimizing the control for both over a driving cycle.
Splines on hollow shafts must meet static and cyclic strength requirements during operation. The demand for maximum utilization of the lightweight construction potential requires precise knowledge of the local mechanical stresses as well as the permissible load capacity of the material, in particular in the area of the splines. In order to ensure both a high static moment as well as a sufficient cyclic strength, the cause-effect relationships between the material properties and the strength properties are examined in torsion tests. The different material properties were adjusted by inductive, neutral and case hardening strategies. In addition, the influence of oil lubrication is analyzed. In this regard, the question is answered as to why oil lubrication has a positive effect on the cyclic strength properties of the splines, although the origin of fractures are in the root fillet of the splines and thus outside the contact area of the edge centered involute splines. The results show that with increasing core hardness an increasing static transfer capability is associated and the surface hardness exerts the greatest impact on the cyclic strength. In addition, it is shown that due to the reduction of friction by an oil lubrication between the connection partners, a reduction in stress in the tooth root fillet is accompanied and thus the cyclical strength of the splines can be increased.
A consideration of multiaxial loads is already implemented in the fatigue strength verifications of drive train components according to current design guidelines and standards. However, present experimental investigations on shaft-hub-connections manifest a need of more critical handling in fatigue calculation in the framework of these user friendly methods based on nominal stress. Non-proportional stresses effected by the superimposed dynamic torsion loads with rotating bending can lead to up to 50% abbreviation in estimation of fatigue limit of press-fit connections. Insufficient consideration of this effect is presently hidden behind high security factors of the stress analysis and can lead to oversizing of machine parts. Therefore, current work presents the findings in fatigue of multiaxial loaded press-fit-connections.
Hereby is described so called HIP process for the production of wear-0resistant, corrosion--resistant composite materials. The power is transmitted through a shaft on which the composite materials in various geometries and materials are installed depending on the required function. The advantages of manufacturing ifo composite parts are shown with different hardnesses outside and inside. As a custom-made construction of a cooled gear pump is given here as example.
Simple design methods are often used to decrease the pressure peaks in the interstice of press fits but usually the optimization results are nonsatisfying. In this paper the design flexibility of additive manufactured hubs is used to optimize the pressure in the interstice of press fits. With inlying structures the stiffness of the hub can be influenced locally. As a consequence the pressure in the interstice can be adjusted to an uncritical level. With the method of finite elements different inlying structures are compared in their stiffness-behavior. The optimized results of a stiffness investigation can be transfered directly to the press fit. Experimental results confirmed the numerical conclusions.
Interference fits with knurled shaft are an alternative to normal press-fit-connections. They are combining the advantages of frictional and positive locking shaft-hub-connections. These connections allow the increasement of the transferred loads with constant overall size. In practical applications the manufacturing of the knurling on the shaft of the shaft-hub connection can lead to problems. The following article is meant to provide a possibility to improve the practical application of interference fits with knurled shaft.
