Heavy-duty mobile machines (HDMMs) are a wide range of machinery used in diverse and critical application areas which are currently facing several issues like skilled labor shortage, poor safety records, and harsh work environments. Consequently, efforts are underway to increase automation in HDMMs for increased productivity and safety, eventually transitioning to operator-less autonomous HDMMs to address skilled labor shortages. However, HDMM are complex machines requiring continuous physical and cognitive inputs from human-operators. Thus, developing autonomous HDMM is a huge challenge, with current research and developments being performed in several independent research domains. Through this study, we use the bounded rationality concept to propose multidisciplinary collaborations for new autonomous HDMMs and apply the transaction cost economics framework to suggest future implications in the HDMM industry. Furthermore, we introduce a conceptual understanding of collaborations in the autonomous HDMM as a unified approach, while highlighting the practical implications and challenges of the complex nature of such multidisciplinary collaborations. The collaborative challenges and potentials are mapped out between the following topics: mechanical systems, AI methods, software systems, sensors, connectivity, simulations and process optimization, business cases, organization theories, and finally, regulatory frameworks.
Heavy-duty mobile machines (HDMMs) are a wide range of machinery used in diverse and critical application areas which are currently facing several issues like skilled labor shortages, poor safety records, and harsh work environments. Consequently, efforts are underway to increase automation in HDMMs for increased productivity and safety, eventually transitioning to operator-less autonomous HDMMs to address skilled labor shortages. However, HDMMs are complex machines requiring continuous physical and cognitive inputs from human operators. Thus, developing autonomous HDMMs is a huge challenge, with current research and developments fragmented into several independent research domains. Furthermore, autonomous HDMM technologies are a stack of several technologies requiring a convergence of diverse competencies from the different domains. Through this study, we provide an overview of the HDMM industry and use the bounded rationality concept to propose multidisciplinary collaborations for new developments in autonomous HDMMs. Furthermore, we apply the transaction cost economics framework to highlight the conceptual challenges and implications of these collaborations. Therefore, we bring together several domains of the HDMM industry to introduce autonomous HDMMs as a general and unified approach. The collaborative challenges and potentials are mapped out between the following topics: mechanical systems, AI methods, software systems, sensors, connectivity, simulations and process optimization, business cases, organization theories, and finally, regulatory frameworks. In doing so, we highlight the need for new and multidisciplinary perspectives that should be considered by academic and industrial practitioners working on the development and deployment of autonomous HDMMs.
Electrifying vehicles yields advantages such as reduced emissions, better performance and more flexibility. While electric machines can directly drive the wheels or tracks of heavy-duty mobile machines (HDMMs), the implements require a combination of electrics and hydraulics for robust, high-force linear actuation. This survey focuses on different of such electro-hydraulic implement systems that have been proposed by industry and academia over the last decades. For the hydraulic circuits, centralized valve-controlled architectures are identified as less progressive but easy to implement for a fast market penetration, while novel decentralized circuit concepts can be more efficient but also more challenging for HDMMs compared to stationary or aircraft applications. The electric machine (EM)-pump combinations are mostly formed out of standard components so far, while customized, integrated or even linear-pump concepts offer room for improvement. Different forms of non-stationary electric energy supplies were also found to be numerous, but many technologies require more development.
We propose a loosely-coupled framework for integrated task assignment, motion planning, coordination and control of heterogeneous fleets of robots subject to non-cooperative tasks. The approach accounts for the important real-world requirement that tasks can be posted asynchronously. We exploit systematic search for optimal task assignment, where interference is considered as a cost and estimated with knowledge of the kinodynamic models and current state of the robots. Safety is guaranteed by an online coordination algorithm, where the absence of collisions is treated as a hard constraint. The relation between the weight of interference cost in task assignment and computational overhead is analyzed empirically, and the approach is compared against alternative realizations using local search algorithms for task assignment.
A load sensing (LS) supply in combination with control valves is one of the most common solutions for the actuation of implements on heavy-duty mobile machines (HDMMs). A major drawback of this approach is its relatively low energy efficiency due to metering losses—especially for multi-actuator operation and load braking. Several novel, more efficient concepts have already been proposed but involve high component costs for each actuator, which is not acceptable for HDMMs with many actuators that have a medium to low energy turnover. Therefore, this work proposes a novel system design which is based on a conventional LS system—for cheap operation of a high number of low-energy-consuming actuators—but allows to avoid metering losses for single high-energy-consuming actuators by replacing their metering valves with electric-generator-hydraulic-motor (EGHM) units that work similar to pump-controlled concepts. The benefits of the novel concept are explained in detail by looking at the three main throttling functions of an actuator in a typical valvecontrolled LS systems, which the novel concept avoids by applying pressure in the actuator return lines and recuperating energy electrically instead of dissipating it by throttling. Furthermore, advantages and challenges for the novel concept are analyzed, and ways to address the latter are presented. Before the novel concept is simulated, the required control algorithms are presented. The simulation study in Amesim and Simulink focuses on a telehandler that utilizes the novel concept for the boom, extension and tilt actuators. Simulation results show that the novel system can decrease the required input energy for typical duty cycles by up to 34% compared to a conventional LS system. At the same time, simulations show that, from an economic perspective, it seems most reasonable to utilize the novel EGHM units only for the boom and extension actuators of the studied telehandler.
In recent years, a variety of novel actuator concepts for the implements of heavy-duty mobile machines (HDMMs) has been proposed by industry and academia. Mostly, novel concepts aim at improving the typically low energy efficiency of state-of-the-art hydraulic valve-controlled actuators. However, besides energy-efficiency, many aspects that are crucial for a successful concept integration are often neglected in studies. Furthermore, most of the time, a specific HDMM is focused as an application while other HDMM types can show very different properties that might make a novel concept less suitable. In order to take more aspects and HDMM types into account when evaluating actuator concepts, this paper proposes a novel evaluation algorithm, which calculates so-called mismatch values for each potential actuator-application match, based on different problem aspects that can indicate a potential mismatch between a certain actuator concept and an HDMM. The lower the mismatch value, which depends on actuator characteristics as well as HDMM attributes, the more potential is the match. At the same time, the modular nature of the algorithm allows to evaluate a large number of possible matches at once, with low effort. For the performance demonstration of the algorithm, 36 potential matches formed out of six actuator concepts and six HDMM types are exemplarily evaluated. The resulting actuator concept ratings for the six different HDMMs are in line with general reasoning and confirm that the evaluation algorithm is a powerful tool to get a first, quick overview of a large solution space of actuator-HDMM matches. However, analyzing the limitations of the algorithm also shows that it cannot replace conventional requirements engineering and simulation studies if detailed and reliable results are required.
For the longest time, valve-controlled, centralized hydraulic systems have been the state-of-the-art technology to actuate heavy-duty mobile machine (HDMM) implements. Due to the typically low energy efficiency of those systems, a high number of promising, more-efficient actuator concepts has been proposed by academia as well as industry over the last decades as potential replacements for valve control-e.g. independent metering, displacement control, different types of electro-hydraulic actuators (EHAs), electro-mechanic actuators or hydraulic transformers. This paper takes a closer look on specific HDMM applications for these actuator concepts to figure out where which novel concept can be a better alternative to conventional actuator concepts, and where novel concepts might fail to improve. For this purpose, a novel evaluation algorithm for actuator-HDMM matches is developed based on problem aspects that can indicate an unsuitable actuator-HDMM match. To demonstrate the functionality of the match evaluation algorithm, four actuator concepts and four HDMM types are analysed and rated in order to form 16 potential actuator-HDMM matches that can be evaluated by the novel algorithm. The four actuator concepts comprise a conventional valve-controlled concept and three different types of EHAs. The HDMM types are excavator, wheel loader, backhoe and telehandler. Finally, the evaluation of the 16 matches results in 16 mismatch values of which the lowest indicates the "perfect match". Low mismatch values could be found in general for EHAs in combination with most HDMMs but also for a valve-controlled actuator concept in combination with a backhoe. Furthermore, an analysis of the concept limitations with suggestions for improvement is included.