Adams Simulation Incorporated DOE to Help Design Robot with Human Motion MSC Software | CASE STUDY Case Study: Kyusyu Sangyo University Overview One of the most prominent areas of focus in the robotics industry today is the design of more human-like robots. Giving human features to robots offers tremendous advantages compared to traditional designs; for example, some robots are now designed with human-like legs rather than wheels, which enables them to move more easily in dangerous environments and over obstacles. These bio-inspired robots also provide a testing ground for new medical technologies, such as the development of artificial muscles. This technology would give scientists insights into damaged limbs and help them develop new cures for patients to recover lost motor functions. Researchers at Japan’s Kyusyu Sangyo University have been researching the benefits of designing robots with more human features. MSC Adams was their simulation tool of choice, and its Design of Experiments (DOE) capabilities were instrumental in helping them further refine their designs. Based on an interview with Dr. YongKwun Lee, Professor in Department of Biorobotics, Kyusyu Sangyo University, Japan
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Adams Simulation Incorporated DOE to Help Design Robot with Human Motion
MSC Software | CASE STUDY
Case Study: Kyusyu Sangyo University
OverviewOne of the most prominent areas of focus in the robotics industry
today is the design of more human-like robots. Giving human
features to robots offers tremendous advantages compared to
traditional designs; for example, some robots are now designed with
human-like legs rather than wheels, which enables them to move
more easily in dangerous environments and over obstacles.
These bio-inspired robots also provide a testing ground for new medical
technologies, such as the development of artificial muscles. This technology
would give scientists insights into damaged limbs and help them develop new
cures for patients to recover lost motor functions.
Researchers at Japan’s Kyusyu Sangyo University have been researching
the benefits of designing robots with more human features. MSC Adams
was their simulation tool of choice, and its Design of Experiments (DOE)
capabilities were instrumental in helping them further refine their designs.
Based on an interview with Dr. YongKwun Lee, Professor in Department of Biorobotics, Kyusyu Sangyo University, Japan
“The ADDAM robot demonstrated human-like walking capabilities and met all of our other design objectives.”
Dr. YongKwun Lee, Professor in the Department of Biorobotics in Kyusyu Sangyo University
Challenge
Researchers at Kyusyu Sangyo University developed a two-legged human inspired robot called ADDAM (Android with Digital Dream for Advanced Machine). The robot has two degrees of freedom (DOFs) at each ankle, one DOF at each knee, and three DOFs per hip. Each actuator is driven by a 2-watt DC motor. The robot is 60 cm high and weighs 11 kg. The team has also developed a robotic arm driven by a micro electro-hydraulic actuator (Micro-EHA) system.
In the human body, muscles are attached to bones which are connected to joints. The developers of ADDAM borrowed this concept. In ADDAM each link is connected to each joint and not to the actuators. This model is a more accurate representation of the bending and walking functionality of the human knee. As shown in the figure
Key Highlights:below, the structure is composed of two links connected by a revolute joint with a linear actuator positioned parallel to the links. This structure allows for a bending movement, similar to that of a human muscle. This approach makes it possible to achieve a relatively larger torque with a small motor.
The human body can move in a variety of ways due to our intricate skeletal framework. ADDAM’s bio-inspired design encompasses complex motion profiles that make it difficult to design. Engineers had to ensure that the sizing of the links and actuators were accurate in order to achieve the needed working range that represents a human motion.
To provide a sufficient range of motion, the actuators are configured in an offset structure as shown in the figure below.
Actuator design in ADDAM is based on human musculature
Closed link mechanism used in ADDAM
Interference between link and actuator limits maximum bending angle of robot
Maximum bending angle as a function of actuator length as predicted by Adams
Offset avoids interference on pitch DOF of hip
Structure of parallel link mechanism
Product: Adams implementation of DOE
Industry: Robotics
Benefits:
• Adams simulation results achieved good correlation with physical measurements
• Design of Experiments was applied on the robot model to optimize each design parameter using Adams
• Prototypes of the ADDAM robot and the robotic arm were built and performed as predicted by the simulation with a high degree of fidelity
This further increases the complexity of the structure and number of design parameters that need to be optimized.
Solution/Validation
Kyusyu Sangyo University researchers addressed these complex design challenges by simulating the design of the robot with MSC’s Adams multibody simulation software.
Researchers modeled the initial concept design of each of the robots in Adams and then used design of experiments (DOE) to optimize each of the design parameters. The figure above shows how the researchers used Adams simulation to set the length of the actuator Lk in the ADDAMS robot.
Fine tuning of actuator length
Biorobotic inspired robotic arm from Kyusyu Sangyo University shaking hands with a person
The design of the robot arm
SC Adams Result - Rolling motion simulation with robot carrying a 2 kg load
Simulation predictions vs physical measurements of ZMP
MSC Adams Simulation of the ADDAM robot walking over an obstacle
Utilizing DOE, Adams was configured to iterate through Lk values from 70 mm to 210 mm and calculate the maximum bending angle for each value. The results above show that as Lk increases, maximum bending angle increases. However, at the maximum actuator length of 210 mm the bending angle is suddenly reduced since the actuator itself interferes with the motion. The figure shows that the optimal value for Lk is about 170 mm.
The final parametric design step involved simulating values around the approximate optimum values determined in the previous parametric simulation to find the optimum value with a higher degree of precision.
As shown in the figure above, dynamic simulation was performed with six values for Lk between 173 mm and 180 mm. The simulation showed that Lk = 177.5 provides a maximum bending angle of 70o which is sufficient for stable walking. The other design parameters on the robot were selected in the same way.
Multibody simulation was used to simulate the performance of the complete ADDAMS robot design to help predict different forms of inertia that it would typically face:
• Linear inertia
• Rotary inertia
• Inclination
• Ground Reaction Force
Simulation was also used to predict the zero moment point (ZMP), the point on the ground where the sum of all of the moments of active forces is equal to zero. ZMP is useful in determining the robot’s stability. ZMP was also measured by physical experiments and the simulation
For more information on Adams and for additional Case Studies, please visit www.mscsoftware.com/adams
robot demonstrated human-like walking
capabilities and met all of our other design
objectives. The robotic arm can lift an
object greater than 5 kg even though its
own mass is only 2.2 kg.” - YongKwun
Lee, Professor in the Department of
Biorobotics in Kyusyu Sangyo University.
Researchers are planning to improve on
the design of ADDAM by using multibody
simulation to further improve the capabilities
of ADDAM, such as by enabling it to perform
fast walking, running, jumping, turning, and
lifting heavy weights.
About Kyusyu Sangyo University
Kyusyu Sangyo University is located in
Fukuoka City, Japan and has over 10,000
students. Students in the Department of
Biorobotics are first taught the underlying
theories and processes of robotics and
consumer electronics. Once they have
acquired this fundamental knowledge
they can then hone their field-specific
expertise by focusing on leading-edge
technologies such as robotics and
medical/assistive technologies.
predictions matched up closely to the physical measurements. Researchers found that the Adams simulation had a strong positive correlation to that of physical test results, meaning it would be able to handle treacherous terrain.
The results of the DOE & Optimization study provided researchers with the information they needed to come up with a robust design that matches with physical testing.
Physical experiments correlated extremely well with the simulation results for ADDAMS, that researchers at Kyusyu Sangyo University used MSC Adams to design a bio-inspired robotic arm. Team utilized the Adams software and DOE to optimize the link parameters in the design. After optimizing the design, they confirmed its performance by simulating a rolling motion at the shoulder with the robot carrying a 2 kg mass. The physical experiments proved that their design can embody the motions made by a human arm.
Results
“Prototypes of the ADDAM robot and the robotic arm were built and performed as predicted by the simulation with a high degree of fidelity. The ADDAM
