Solon, OH — May 27, 2022– Transporting heavy sensitive payloads over land has always been a challenge due to the intricacies of terrain changes. As part of an Autonomous Field Supply Vehicle (AFSV) project, Kyntronics provided 18 actuators for customer; RMD Systems, to help meet those challenges. The AFSV project was being developed for transporting sensitive payload in potential military applications, and it needed help with gait control for a large legged robotic platform.
The walking vehicle capabilities and requirements were to transport a payload of over 2,000 lbs. that would be extremely sensitive to shock and vibration. RMD needed an actuator capable of providing high force in a small package and energy efficient while being rugged enough for outdoor use. In addition to meeting the force requirements, Kyntronics SMART Electro-Hydraulic Actuator (SHA) was able to match the criteria for power efficiency and was able to tolerate high shock loading.
Kyntronics collaborated with RMD on the complex actuator requirements that were necessary to allow the vehicle to control the pitch and roll angles and body height of the vehicle during the walking cycle. In addition, the AFSV was developed to be capable of autonomous behaviors including recovery gait, putting the body on ground, leveling the body independent of the terrain, and using an autopilot system onboard to control the vehicle.
The actuators were used on the Leg Nodes. This provided several capabilities including allowing the operator to:
- Manipulate each leg joint individually using ‘single leg mode’
- Reposition the legs or use the legs as manipulators to move objects
- Control the platform position
- Integrate with the sensor system to determine position changes
With support from Kyntronics, RMD successfully designed, built, and tested the AFSV in 20 months from project kickoff. Kyntronics provided three configurations of actuators based on the force and speed requirements of the specific leg joints (Coxa, Femur, and Tibia joints). The actuators were integrated with RMD’s gait engine control software, which uses position and force feedback from the actuators to control the legs and the body of the vehicle. The system has demonstrated omni-directional walking, six DOF body control, and operation on various terrain types while carrying a simulated payload.
Coxa actuator (Figure 2) is responsible for rotating the leg around its vertical axis (analogous to the hip joint). A linkage was used to transform the 6” stroke of the actuator into 180 degrees of rotation.
The femur actuator (figure 3) is installed on the leg. The femur actuator was installed on its side to reduce the overall thickness of the vehicle. By installing the femur actuator inside the coxa structure, RMD was able to reduce the inertia of the leg, improving the walking performance.
The tibia actuator (Figure 4) was installed in the last active leg joint. The tarsus joint (which is attached to the foot) is driven by a bellcrank mechanism that keeps the foot perpendicular to the ground without requiring active control. A position sensor was mounted on the side of each actuator to provide position feedback on the rod position of the actuator. The data from the position sensor was then used to calculate the overall pose of the leg. Additionally, the force in each cylinder was monitored to ensure that the loads on the legs were maintained within safe limits.
Kyntronics SMART electro-hydraulic actuators installed on these three critical leg joints delivered the force density and durability of a hydraulic solution while being energy-efficient and eliminating the leak risks inherent with hydraulics. This innovative actuation solution also provided the low mass and ease of system integration characteristics of an EMA solution. Additionally, the valving inside the Kyntronics actuator allowed the actuators to hold a static load without consuming any power.
Kyntronics, established in 2013, specializes in actuation systems. Our products facilitate the global trends of increased automation, higher precision control of manufacturing processes, lower costs and IoT connectivity. Our mission is to offer the best combination of mechanics, electronics, software and support in actuation and motion control products.