Off road terrain poses a continual challenge to military movement. To meet this challenge, a robotic mule is designed to be a personal mobility device that can carry a soldier or that a soldier can carry. This paper will discuss the design process of such novel robotic mule, including overall structure, cargo/soldier platform, driving system, power system, and stress analysis and simulation. This robotic mule provides a new approach for army soldiers or soldiers’ equipment to move across field effortlessly and efficiently. The movement of the robot can be guided by GPS system or follow a soldier who carries emitter with sensor. The robot is designed to operate in nature terrain, which is standard nature trail in a boreal forest and may have a few roots and rocks but free from climbing obstacles.
The robotic mechanism is suitable for one-man lift, with weight not to exceed 20 kg. The robot is capable of moving through a standard door width 80 cm while fully loaded. The system can support 100 kg payload. It also provides soldier following capability and be able to perform with or without the operator on board. The system controls balance of the vehicle, while avoiding obstacles, and negotiating narrow urban or off-road terrain. The speed on flat terrain is 5–7 m/s with a range of 30 km.
The robot mule consists of a robust chassis platform, a driving system, a power system, a chair system for soldier, and GPS and vision system for autonomous control. For chassis platform, its structure is designed to be both light and sturdy. Stress analysis of the structure is applied to verify the safety of carrying objective payload. The width of the chassis platform is designed to access standard handicap door. For driving system, considering both terrain and weight limits, a four-wheel driving system is designed to overcome nature terrain which may have a few roots and rocks. Next, based on calculation of traction need and travel range, motor and lithium battery kit are selected to maintain target speed on flat terrain with target mileage. Power for extra functional features needed, such as sensors for navigation and surrounding detection etc. is also considered in calculation of battery capacity. Cargo/soldier platform is designed to provide proper space for carrying the soldier and/or equipment. Security fixtures are designed and added to the cargo/soldier platform which avoid swaying and falling of equipment. Also, ergonomics research is conducted to make a comfortable and hazards free platform for soldiers. Moreover, two handles are designed and will be mounted on each side of the robot mule, which makes the robot be lifted easily by a soldier and helps guard cargo payload in place.