When we think of robots, a big picture of the bulky machines comes to our mind. People often have this perception of robots which is not bad because robots can vary from as small as an ant to as big as dinosaurs. You can literally see dinosaur-sized robots in universal picture studios. Talking about robots, they have their world within. They are composed of mechanical, electronics and software components. For proper functioning, all these components should work in coordination. It is not that easy to build a robot as it is a multidisciplinary sector. If you want to build one you are supposed to be familiar with these sectors. Today, robots have got their body and a complex set of electronic components with a code to execute the commands. The robotics industry is booming across the world creating new milestones every day. The Global Robotics Market was valued at USD 27.73 billion in 2020 and is expected to reach USD 74.1 billion by 2026. They not only perform risky tasks but also create new opportunities across the globe. There have been races globally to develop the best robots. In 2012, Boston Dynamics developed the Cheetah- a four-footed robot that can run and jump. Similarly, Hansen Robotics has made a humanoid robot named Sophia depicting the future for AI. These robots can be used for entertainment, military, rescue, manufacturing, education, etc. to name a few.
The physical portion of the robot is generally composed of mechanical components. It includes structure, mechanisms, drive, actuators, mechanical sensors, etc. Moreover invisible parts like control systems, efficiency, power, cooling, sensing environmental factors also come under mechanical parts. Not only that, the kinematics of the mechanisms and robot, degree of freedom, limits and vulnerability and the tasks robot can do are all determined by the mechanical portion of the robot. The mechanical work is not limited to these areas, it can differ with the types and specialization of robots. Mechanical engineering can be applied in robotics in a wide range of areas. For simplicity and ease of our learning, we can classify this vague area into different parts. Some of the main parts are:
The main component of a robot is its structure. The structure not only shapes the robot but also determines the task it can do. The design of proper structure helps to function properly otherwise it will result in a failed performance which is not desired. The structure may be determined at the end i.e. after the selection of mechanism and size analysis. The selection of materials, design and study of efficiency should be done within the economic boundaries. Various computer-assisted tools like CAD (Computer-Aided Design like AutoCad, Solidworks), CAE(Computer-Aided Engineering like Matlab, Ansys), CAM (Computer-Aided Manufacturing like CNC machining, 3D printing) are used to get the optimum design. After prototyping and testing, the structure is manufactured using a suitable manufacturing process. The structure is supposed to make robots robust, give them an aesthetic look as well as contain the overall load of robots. Structure design could be different for mobile robots and fix positioned robots like industrial. Great care has to be given while designing the structure so that it doesn’t look bulky and over defined.
The mechanism is selected based on the purpose of the robot. The purpose of making robots is to assess tasks to them. A task of a robot is composed of different motions like linear, rotating, vibrating and others. So different mechanisms can also be combined to get a single desired motion. Such as a robotic arm is designed with different mechanisms involving rotational motion from the motor and linkages are used to get the desired path for the end effector. The same task can be done by different combinations of mechanisms so optimum is selected through power, manufacturing process and economic consideration. One designing the mechanism should perform the kinematic analysis of the mechanism, power calculation, study the manufacturing process of the parts, etc. A good and minimalistic mechanism could be time-efficient, reduce the cost of manufacturing and overall performance of the machine. A large investment is made for the design of mechanisms in the industry so the best design of mechanism could save a lot of capital and money.
Mobile robots have wheels, legs or propellers to move from one place to another. The type of drive is also selected based on the type of manoeuvre of the robot. A robot requires a drive system to move its body, arm or wrist. Different types of drive systems are available. From electronic drive system to hydraulic for large-sized robots. For example, if the robot has to move in a plane or surface, wheels are used. There are different types of wheels you can use in your robots based on your need. If a simple motion is needed, you can use differential and mecanum or omni wheel for an omnidirectional movement. Similarly, if a robot has to jump or walk in any terrain, legs are used. Legs don’t mean actual legs, the dynamics of the human legs are obtained using different drive systems which are well-suited for rotational joints as well as linear joints and added to the robot. Motors and other actuators are used to drive wheels and mechanisms to give desired motion.
Actuators are the main part of any mechanical system often termed as the muscle of the robots as it is the source of motion in any mechanism, functional features such as Degrees of Freedom(DOF), speed, accuracy, load-bearing capacity, etc. Different types of actuators are available based on their purposes such as electronic actuators, hydraulic actuators and pneumatic actuators. Electronic actuators like servo motors, stepper motors or direct-drive electric motors are used as required by the mechanism. Similarly, hydraulic actuators deliver high power and are used in high-end robots. Last but not least pneumatic actuators use compressed air as their source. The latter two are mostly used for linear actuation. Power is transmitted directly as well as indirectly to the mechanism and driving system. Battery, compressed air, etc. are the source of power for actuators in mobile robots.
Sensors and Encoders
Sensors or Transducers are those components that give continuous data of environmental factors of robot surroundings which help the robot to calculate its position, orientation and detect obstacles, change in temperature, etc. Encoders give data on the position of the various components inside the robot. Encoders are fed into moving objects which generate an electrical signal which is further processed to obtain the position of that object. Although Sensors and Encoders are completely different components, we put them together to know the basic principle i.e. feedback control system. In this system, sensors and encoders continuously give feedback to the robot’s processing system and decide what to do next. Since the capability of the robot is not only to have the desired motion and efficiency, it has to do every task one after another seamlessly. So all components mechanical, electronic and software are equally important in robotics.