Most popular to get rid of cables and remove limbs

2022-08-02
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Get rid of cables, remove limbs, NASA humanoid robot, female warrior rush to disaster scenes for human beings

original to avoid friction; For the part of force measurement, the heart of synced machine

the heart of the machine is divided into two parts. Everyone knows how to go along this route to analyze the division network

analyst: Wu Jiying

: Joni Zhong

this paper gives a detailed explanation of the Valkyrie humanoid robot developed by NASA, including the difference between this robot and Robonaut 2, algorithm and technology, and task completion. It is believed that readers will have a clearer understanding of the research and development background, construction algorithm and application of future scenarios of Valkyrie humanoid robot

humanoid robot is the embodiment of human beings. It can traverse rugged terrain, enter narrow channels and narrow spaces in kinematics, move objects, reach high places, and complete many other tasks such as improved explosive device (IED). In this paper, we discuss NASA's Valkyrie humanoid robot. Figure 1 shows the latest Valkyrie captured by IEEE spectrum during its field visit to NASA's Johnson Space Center (JSC)

figure 1 valkyrie. Photo: Evan ackerman/ieee spectrum[1]

jsc was founded in 1961. JSC's scientific and engineering activities have been centered on NASA's manned space program. Even today, space flight is still an extremely dangerous attempt. Therefore, in recent years, JSC has devoted itself to the design and development of humanoid robots that can interact with humans. Such robots have the same strength and speed as humans working in space. The robot will work near the astronauts as their assistant [12]

in the mid-1990s, when this research project was conceived, human and robot working together was just a new concept that had just begun to be explored in academic laboratories. In order to prove the effectiveness of robots using human tools, a double arm test-bed called dart was built. By 1999, with the help of the Defense Advanced Research Projects Agency (DARPA), the dexterous Robotics Laboratory (DRL) had built its first upper limb humanoid system, Robonaut 1 (R1). Since then, DRL has gradually become a world-famous robot laboratory, designing and equipping more than ten unique robot platforms. The most familiar one is robonaut2 (R2). R2 has a human trunk, head and arm. Currently, it is performing a well-known high-risk "spacewalk" activity on the international space station, that is, it can use relevant tools and tool operating systems during extravehicular activities (EVA). R2 has many advantages in the microgravity environment in space, but it is not suitable for walking on the earth

robonaut 2 (R2) is a robot developed by a very successful public-private partnership between General Motors (GM) and NASA. R2 whole body contains 42 degrees of freedom (DOF). Among them, each arm has 7 degrees of freedom, the neck has 3 degrees of freedom, each hand has 12 degrees of freedom, and the waist has 1 degree of freedom (see Figure 2 (a)). Recently, R2 received a mobile upgrade in the form of "climbing legs", which will enable it to move in the international space station and expand its operational capabilities. This is also the earliest version of Valkyrie before 2012 (see Figure 2 (b))

figure 2 R2 figure [12]

valkyrie is not a robot designed for space, but a robot designed for disaster scenes on earth. About the design purpose of Valkyrie, the project leader introduced as follows:

"NASA's space exploration goal is to reach Mars. In order to reach Mars, NASA is likely to send Robots before human explorers. When humans arrive, these robots can work with humans. Valkyrie will be used in the project of exploring Mars" [1]

"NASA is committed to the operation and capability innovation of current and future humanoid robots, especially the task execution related to space exploration missions. NASA's interest in humanoid robots stems from their potential ability to efficiently operate equipment and their ability to effectively operate as astronaut assistants. NASA's interest in using humanoid robots in extreme space environments is also similar to the potential of similar robots in ground applications such as disaster relief Overlap in use. " [2]

valkyrie is much more than an updated version of R2 with legs. R2 has begun to explore supervised autonomy, while Valkyrie can complete tasks under more stringent delay and bandwidth constraints, which means that it is more intelligent and has a lot of embedded intelligence. Valkyrie is a brand-new robot with brand-new technology and brand-new unique appearance. Valkyrie has the ability of walking, balancing and manipulating. The research on Valkyrie focuses on developing complex behaviors to improve the autonomy of biped humanoid robots. So, what is the difference between Valkyrie and R2

1. The difference between Valkyrie and R2

valkyrie's whole body contains 44 degrees of freedom. The arm has seven degrees of freedom, the wrist and hand can complete the action, and each hand has three fingers and a thumb, so its hand has six degrees of freedom. It has a head with three degrees of freedom that can tilt and rotate, a waist (torso) with three degrees of freedom that can rotate, legs with six degrees of freedom, and feet equipped with six axial force torque sensors. There are series elastic actuators (SEA) in the arms, trunk and legs. These brakes can achieve torque control with a bandwidth of up to 70Hz. The neck is controlled by position, and the fingers driven by tendons are controlled by current. In addition to the absolute position encoder, incremental encoder and spring deflection sensor in the sea, the robot uses micro strain inertial measurement unit (IMU) sensors in the pelvis and torso, uses an ATI force torque (F/T) in the sole of each foot to estimate the center of pressure (COP), and uses multiple sensors for lidar and stereo data

unlike previous NASA robots, Valkyrie is battery powered and can operate without tying cables. The portable battery in the backpack can last for an hour, and it only takes a few minutes to replace the battery. In addition, Valkyrie's limbs can also be removed, and it only takes a few minutes to replace the arm, because the structure of the left arm and the right arm are exactly the same, and even the left arm can be directly replaced with the right arm. Valkyrie is equipped with an amazing number of sensors: cameras and lidar are in the head, more cameras and sonar are in the abdomen, and more cameras are in the forearms, knees and feet. The data collected by the sensor will not be transmitted to the operator of Valkyrie at the same time. Instead, it will determine which sensor's data is the most important according to the current task, and transmit the most important data to the operator as soon as possible, which will help Valkyrie to complete its independent work quickly and efficiently

r2 and Valkyrie both chose the decentralized control scheme, but it was not until the Valkyrie project that the "perfect torque source" required by the decentralized control scheme was generated. R2 adopts proportional derivative control loop to obtain good torque tracking results. However, it does not adjust the disturbance detected in each actuator. Researchers have done a lot of work in improving the embedded control performance of Valkyrie, and improved the series elastic actuation (SEA) technology. Disturbance observers (dobs) can significantly enhance the torque tracking ability of sea in the face of variable inertia load and other disturbances

r2 uses a customized motor control board called "superdriver". It is composed of field programmable gate array (FPGA), in which a PowerPC processor coupled with three-phase inverter is embedded. This combination on a single board allows it to operate motor commutation and current control, serialization and deserialization of joint data and commands, and sensor processing. This design was later improved to R2 mobile upgraded climbing leg. On this basis, turbordriver is introduced to repackage the function of the super driver into two independent printed circuit boards, including a high-voltage drive circuit and a logic board to process the sensor, embedded control algorithm and communication with the central control computer, and a FPGA to process the motor commutation. The two boards are then stacked together, reducing the overall footprint and allowing each board to adapt to specific project needs. In the Valkyrie project, the modular design of the turbine engine is still used. The power plate has been redesigned, including a forced air cooling bridge, which can provide short-term high torque of more than 30A continuous and 60A. Although all joints of R2's climbing legs are dedicated to the use of turbine drivers, Valkyrie uses turbine drivers on most major joints, while other custom boards are used on smaller joints such as wrist, hand and neck

the avionics structure of R2 was designed to reduce interconnections, especially those that span degrees of freedom, thereby creating robonet. Robonet is a high-speed, two-wire, multi-point data network, which follows the master-slave communication protocol

robonet the channel that connects the super or turbine engine to the master node. One channel is dedicated to the two-wire conductor of one limb. The master node is connected to the master computer through PCI (R2) and PCI Express (Valkyrie) and implemented on FPGA. Data is transferred from the host PC to the user space of Valkyrie through PCI bus call (R2), or using direct memory access (DMA) and dedicated shared memory area. The robonet protocol is similar to the inter integrated circuit (I2C) protocol. After upgrading to Valkyrie, each memory address can be updated at the speed of 1kHz, and each channel can reach 4mb/s

II. Algorithms and technologies in Valkyrie

when we understand these differences, let's see what algorithms and technologies are applied in Valkyrie

1. Walking and operation

valkyrie uses a quadratic program (QP) as a momentum based whole-body control algorithm [13]. QP was first applied to the walking algorithm of atlas robot of Boston Dynamics. Its main purpose is: after the robot takes one step, the whole body control algorithm based on momentum calculates the foothold available for the next step. The input of QP is the desired motion, acceptable external force and acceleration in the task space. The objective function is optimized by tracking a desired rate of change of centroid momentum and minimizing joint acceleration and contact force. The objective function of QP algorithm is:

where a is the centroid momentum matrix (CMM), WG is the gravity wrench, and W_ GR, I is the ground reaction wrench applied to the robot body due to the contact between the body and the environment, w_ Ext, I are other external forces exerted on the robot. The output V of QP is a joint acceleration vector and contact wrench used to calculate the required actuator torque. The QP output is then used to calculate the required joint torque using the inverse dynamics algorithm. Optimize whole body control with QP

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