Robots in Exploration

Introduction to robots in explorations

    

“A robot is defined as a self-controlled device consisting of a combination of electronic, electrical or mechanical units that can function in place of a living agent.”

    

        Exploration Robotics is a field where mobile robots are deployed into natural or artificial situations where humans are unable to go to collect useful data and, in some cases, execute physical activities. It is basically concerned with the utilization of a robot to enhance knowledge over a specific region. 

Defense and Security, Search and Rescue, Archaeology, Environmental monitoring, nuclear decommissioning, Space exploration, and the Oil and Gas sector are just a few of the many situations and applications where exploration robotics has the potential to impact a lot.

Figure 1: Search & rescue and archaeology robots

Space Exploration:

            The field of interest is chosen, so let’s dive into the topic. Robots are crucial in investigating the harsh environment of space. The Moon is the only celestial body that mankind has walked on other than the Earth. Robotic missions, on the other hand, are now able to reach space faster and collect more data than humans because of breakthroughs in research. Robots have their advantages as compared to humans in many ways because they do not tire, can operate in an airless environment, and do not become bored or distracted.

              Robotic arms, for example, come in a variety of sizes and designs (e.g., the Space Shuttle Remote Manipulator System; rovers - Sojourner; landers - Mars Pathfinder; atmospheric probes - Huygens Titan probe; orbiters - Galileo; and planetary flyby probes - Voyagers 1 and 2).

        In all the above-listed robots, a power supply, controller, actuators, sensors, and a radio communication unit are common components found in all space robots. These sensors collect data about the robot and its surroundings; the controller then processes the data and control instructions before sending command signals to the actuators. The signals are converted by the actuators, who then perform the operations.

Types of space robots:

        The two primary types of space robots are Remotely Operated Vehicles (ROV) and Remote Manipulator Systems (RMS).

    A typical ROV rover moves over the landscape after landing, a lander that communicates with an extra-terrestrial plain, or an unmanned spaceship. ROVs are employed by bomb squads to discover potentially hazardous objects at nuclear sites and subsea, in addition to being used by space researchers for terrain exploration in space.

        In industry and production, the RMS is the most prevalent robotic device. It's more like a robotic arm that can mimic human arm movements including up-and-down, side-to-side, and 360-degree circular motion. It can be controlled either by specialized computer software.

 

Robots used in space exploration: 

1. R5, aka Valkyrie

Figure 2: R5, aka Valkyri ( Credit: Nasa )

Originally built by the Johnson Space Center (JSC) Engineering Directorate

Specifications:

Weight: 300 pounds

Height: 6 feet 2 inches

Battery Energy: 1.8kWh

Computers: 2 x Intel Core i7

Degrees of Freedom: 44

Equipped with gripper hands to carry out tasks, and sensors and cameras in head and chest.

Primary function: To carry out repairs such as maintaining solar and electrical panels as well as to explore and collect samples independently.

        

2. Lunar Rover 

Figure 3: Lunar Rover (Credit: ispace, inc)

Designed by Team HAKUTO in Tohoku University’s Space Robotics Lab

Specification:

3.7kg unnamed rover

Shaped like a metallic beetle, lightweight mobility platform decked with 360-degree view 3D cameras 

Primarily designed for surface exploration, can conduct detailed terrain mapping, and the capacity to carry customer payloads to the lunar surface.

An inherent ability to wield tools such as drills and manipulators

3. Dextre

Figure 4: A piece-by-piece look at Dextre, the most sophisticated space robot ever built. (Credit: Canadian Space Agency)

Built by MacDonald, Dettwiler, and Associates, based in Brampton, Ontario.

Height: 3.7 m

Weight: 1,710 kg

About 4oo km above Earth

Primary Work: Robotic arm meant to install and replace small equipment such as outside cameras or the 100-kg batteries used on the Space Station, as well as test new tools and robotics techniques, as well as replace problematic components in the Station's electrical systems

Dextre is currently operated by ground control teams from both the Canadian Space Association and NASA.

Forward and Inverse kinematics

Application: Legged Robots are also used for Space Exploration. An attempt is made to perform the Forward Kinematics and Inverse Kinematics of the (specifically) Leg of the Legged robot.  

Configuration: 3R Articulate robot

Consideration has been made that the body of the robot acts as the base, as the leg will have one joint (initial) fixed to the body.

Frame Assignment: The following image has a skeleton diagram with a frame assigned.

1. First of all, we assign the Z-axis to the all-rotating joints, joint 1 is the cylindrical joint, joint 2 is the revolute joint, joint 3 is the revolute joint. 

2. Then we assign the X-axis to frame L0 at j1(joint-1), in such a way that the X-axis is along with the links and perpendicular to both the Z-axis of L0 and L1. 

3. Y-axis to L0 is assigned using the right rule. Thumb point Z-axis, index finger pointing X-axis, and middle finger pointing Y-axis.    

4. Now we assign the X-axis to L1, as the Z-axis of L1 and L2 are co-planer, X-axis of L1 is assigned away from the Z-axis of L1.

5. The same set of rules are obeyed until you reach the end effector.

6. When we get to the end-effector, we assign the X-axis of the end effector along with link orientation so as to rolling motion, we assign the Y-axis along the Z-axis of base frame to occur yaw motion and assign Y-axis using the right-hand rule.

Figure 5: Skeleton Diagram of the leg of legged robot

DH parameter table: 

1. Link length ai is determined using the distance between the point of intersection of Xi axis with Zi-1 to origin frame along with Xi 
2. Link twist angle αi is determined using the angle between Zi-1 and Zi along with Xi in right-hand sense
3. Joint offset di is determined using distance along Zi-1 axis from origin of frame Li-1 to the intersection of Xi axis with Zi-1
4. Joint angle θi is determined using the angle between Xi-1 and Xi about Zi-1 in right-hand sense

Table.1: DH parameters

Forward Kinematics: For forward kinematics, we provide the angles and calculate the end-effector position.

L₁ = 0.3m                    L₂ = 0.2m              L₃ = 0.15m

Transformation Matrix: The transformation matrices are provided below the standard notations are used.

The X-axis of the end effector has aligned in the positive x-direction of the base frame.

The Y-axis of the end effector has aligned in the positive z-direction of the base frame.

The Z-axis of the end effector has aligned in the negative y-direction of the base frame.

The translation of the end effector is along X-axis with a distance of 0.65m.

Validation via the Python programming via software Pycharm the following images describes that the orientation of end effector and its distance from base matches the answer provided by us.

Code in python for Forward kinematics:

import matplotlib.pyplot as plt

import numpy as np

import pandas as pd

 

print("Forward kinematics with DH paramters as below \n")

data = {'Link length':['0.3','0.2','0.15'],'Link twist angle':['90','0','0'],'Joint offset(m)':['0','0','0'],'Joint angle':['theta1','theta2','theta3']}

df = pd.DataFrame(data)

print(df)

 

print("\nAt Initial conditions the values of theta1 = theta2 = theta3 = 0")

 

R1 = np.array([[np.cos(0),-(np.sin(0)),0,0],[np.sin(0),np.cos(0),0,0],[0,0,1,0],[0,0,0,1]])

T1 = np.array([[1,0,0,0.3],[0,0,-1,0],[0,1,0,0],[0,0,0,1]])

T0_1 = R1.dot(T1)

print("\nT0_1 = \n",T0_1)

 

R2 = np.array([[np.cos(0),-(np.sin(0)),0,0],[np.sin(0),np.cos(0),0,0],[0,0,1,0],[0,0,0,1]])

T2 = np.array([[1,0,0,0.2],[0,1,0,0],[0,0,1,0],[0,0,0,1]])

T1_2 = R2.dot(T2)

print("\nT1_2 = \n",T1_2)

 

R3 = np.array([[np.cos(0),(np.sin(0)),0,0],[-(np.sin(0)),np.cos(0),0,0],[0,0,1,0],[0,0,0,1]])

T3 = np.array([[1,0,0,0.15],[0,1,0,0],[0,0,1,0],[0,0,0,1]])

T2_3 = R3.dot(T3)

print("\nT2_3= \n",T2_3)

 

T0_2 = T0_1.dot(T1_2)

T0_3 = T0_2.dot(T2_3)

print("\nT0_3=\n",T0_3)

Snap of code:

 

Output of the code:

Validating via the software RoboAnalyzer too, the following images describe that the orientation of the end effector and its distance from base matches the answer provided by us.

Figure 6: Simulation in RoboAnalyzer

Here if the frame of the end effector is compared with the base frame, will see that the manual calculations are similar to that of simulation.

 

Inverse Kinematics: Position of end effector is provided such as given below,

a14 = 0.41715287 m

a24 = 0 m 

a34 = 0.013830408 m

Therefore,

Solved via RoboAnalyzer software. 

Figure 7: Inverse Kinematic Solution

The Direct and Inverse Kinematics has been performed successfully.

Conclusion:

Exploration Robotics is a catch-all term in the field of Field Robotics, defining the most real-world mobile robotics applications that aren't covered by Service Robotics or Infrastructure Robotics. Some of the use cases in Infrastructure Robotics are similar to those in Exploration Robotics, while the former provides many more examples that are less repetitious than Exploration Robotics. Exploration Robots, in comparison to Service Robots, must often function in areas that are less organized and more difficult to navigate from a locomotion standpoint.

References:

1.     Piltan, Farzin & Taghizadegan, Ali & Sulaiman, Nasri. (2015), “Modeling and Control of Four Degrees of Freedom Surgical Robot Manipulator Using MATLAB/SIMULINK”, International Journal of Hybrid Information Technology. 8. 47-78. 10.14257/ijhit.2015.8.11.05.

2.     Bliley Technologies, “How are Robots Used in Space Exploration?” Bliley Technologies, Sep 10, 2019, accessed Dec 11, 2021, https://blog.bliley.com/robots-used-in-space-exploration

3.     Kerrie Brooks, “5 robots pushing the frontiers of space exploration” Distrelec, August 17, 2018, accessed Dec 11, 2021, https://www.distrelec.de/current/en/robotics/5-robots-pushing-the-frontiers-of-space-exploration/

4.     “About Dextre“ July 30, 2018, https://www.asc-csa.gc.ca/eng/iss/dextre/about.asp

5.     “Lunar Rover” ispace, https://ispace-inc.com/technology/

6.     “Cave Exploration Robot” Wevolver, https://www.wevolver.com/wevolver.staff/cave.exploration.robot