Mobile robots can be used in many applications, such as carpet cleaning, search and rescue, and exploration. Many studies have been devoted to the control, sensing, and communication of robots. However, the deployment of robots has not been fully addressed. The deployment problem is to determine the number of groups unloaded by a carrier, the number of robots in each group, and the initial locations of those robots. This paper investigates robot deployment for coverage tasks. Both timing and energy constraints are considered; the robots carry limited energy and need to finish the tasks before deadlines. We build power models for mobile robots and calculate the robots' power consumption at different speeds. A speed-management method is proposed to decide the traveling speeds to maximize the traveling distance under both energy and timing constraints. Our method uses rectangle scanlines as the coverage routes, and solves the deployment problem using fewer robots. Finally, we provide an approach to consider areas with random obstacles. Compared with two simple heuristics, our solution uses 36% fewer robots for open areas and 32% fewer robots for areas with obstacles.

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Deployment of mobile robots with energy and timing constraints

Mobile robots are used in many applications, such as carpet cleaning, pickup and delivery, search and rescue, and entertainment. Energy limitation is one of the most important challenges for mobile robots. Most existing studies on mobile robots focus on motion planning to reduce motion power. However, motion is not the only power consumer. In this paper, we present a case study of a mobile robot called Pioneer 3DX. We analyze the energy consumers. We build power models for motion, sonar sensing and control based on experimental results. The results show that motion consume less than 50% power on average. Therefore, it is important to consider the other components in energy-efficient designs. We introduce two energy-conservation techniques: dynamic power management and real-time scheduling. We provide several examples showing how these techniques can be applied to robots. These techniques together with motion planning provide greater opportunities to achieve better energy efficiency for mobile robots. Although our study is based on a specific robot, the approach can be applied to other types of robots

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A case study of mobile robot's energy consumption and conservation techniques

. The world market of mobile robotics is expected to increase substantially in the next 20 yr, surpassing the market of industrial robotics in terms of units and sales. Important fields of application are homeland security, surveillance, demining, reconnaissance in dangerous situations, and agriculture. The design of the locomotion systems of mobile robots for unstructured environments is generally complex, particularly when they are required to move on uneven or soft terrains, or to climb obstacles. This paper sets out to analyse the state-of-the-art of locomotion mechanisms for ground mobile robots, focussing on solutions for unstructured environments, in order to help designers to select the optimal solution for specific operating requirements. The three main categories of locomotion systems (wheeled – W, tracked – T and legged – L) and the four hybrid categories that can be derived by combining these main locomotion systems are discussed with reference to maximum speed, obstacle-crossing capability, step/stair climbing capability, slope climbing capability, walking capability on soft terrains, walking capability on uneven terrains, energy efficiency, mechanical complexity, control complexity and technology readiness. The current and future trends of mobile robotics are also outlined.

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Review article: locomotion systems for ground mobile robots in unstructured environments

Many exploration rovers have been proposed in the past, but none was compared to other systems. Therefore, this paper not only introduces the locomotion concept CRAB, but also compares it to other rovers regarding obstacle negotiation capabilities. Instead of relying only on simulation, a comparison was also performed with real breadboards. In reality the CRAB is compared to RCL-E (Concept E by RCL); the simulations include the MER (Mars Exploration Rover by NASA) as well. The simulations predict significantly superior performance of CRAB compared to RCL-E, which is confirmed by the tests on hardware. The performance of CRAB and MER is similar; however, the CRAB has the same behavior in forward and backward motion because it is a symmetrical structure, while the MER has significantly inferior performance in backward motion.

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Crab - exploration rover with advanced obstacle negotiation capabilities

Power consumption is a key element in outdoor mobile robot autonomy. This issue is very relevant in skid-steer tracked vehicles on account of their large ground contact area. In this paper, the power losses due to dynamic friction have been modeled from two different perspectives: 1) the power drawn by the rigid terrain and 2) the power supplied by the motors. Comparison of both approaches has provided new insight on skid steering on hard flat terrains at walking speeds. Experimental power models, which also include traction resistance and other power losses, have been obtained for two different track widths over marble flooring and asphalt with Auriga- beta, which is a full-size mobile robot. To this end, various internal probes have been set at different points of the power stream. Furthermore, new energy implications for navigation of these kinds of vehicles have been deduced and tested.

Power Consumption Modeling of Skid-Steer Tracked Mobile Robots on Rigid Terrain

This abstract presents a perform study on SOLERO, a new and innovative rover concept for regional mobility on planetary surfaces. A rover is the most suited element to bring scientific instrument to a specific site in order to examine geology, mineralogy or exobiology on extraterrestrial planets. In contrast with the Mars Pathfinder mission, the actual need increases in terms of range and duration. These aspects lead to redesign many aspect of the past rovers, in particular the development of most suitable all terrain performances, autonomous navigation and a new power management concept. In this paper well focus on the locomotion and the energy utilization without contribution of batteries. To validate the SOLERO possibilities in these domains and its use for future planetary exploration missions, modelization, testing and Mars like mission simulation have been done. Due to extreme temperatures the use of batteries is a critical point and becomes too expensive in term of size and mass for long-time missions. In this case, a locomotion concept reducing power consumption with exclusive use of on board power generation has to be investigated. The SOLERO mechanical structure is an optimization of the Shrimp rover developed at EPFL. It has one wheel mounted on a fork in the front, one wheel in the rear and two bogies on each side. The parallel architecture of the bogies and the spring suspended fork provides a high ground clearance while keeping all its 6 motorized wheels in ground contact. This ensures excellent climbing capabilities over obstacles higher that the wheel diameter. Moreover, this original combination of wheeled locomotion and passive adaptation to help to reduce power consumption compared to active design such as legged rovers, without sensible reduction of climbing abilities. To remove the problems linked with energy storage, not only power reduction is important, but also the power management. SOLERO uses exclusively solar cells to generate the electrical power, because its currently the most adapted solution for local energy generation on a rover. However the use of solar power only, have several constraints linked with the incoming solar radiation (insolation). To determine SOLEROs power budget and performances, a Mars insolation and environment model has been chosen as reference. The integrated solar power generation restricts the operation time and power to specific daytime. The electrical power provided by a solar panel of 0.3m2 is over 14W during the four hours around noon, this is sufficient for locomotion. The 1kg scientific payload needs less that 8W power and can be used during a maximal time of height hours during daylight. However, the limited power storage capacities and the reduction of power consumption for locomotion allowed this rover to be small, light and operational during more that 100 sols (Martian days). The total mass is only 10kg and its locomotion performance, in comparison with actual rovers, leads SOLERO to become the perfect candidate for long range mission on near-sun planets

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StÃ©phane Michaud

Papers

SOLERO: Solar Powered Exploration Rover