What are robotic arms/manipulators?
A robotic manipulator is a device that resembles an arm that is attached to a robot's body and used to carry out tasks. Without a manipulator, a robot executing a task would be comparable to someone who had their hands tied behind their back.
The internal construction of robot manipulators is made up of several joints and linkages that are fused together.
There are many uses for robotic manipulators in industry, such as:
- Pick and Place: Robot manipulators are frequently used in the industrial setting for repeated pick-and-place operations like packaging items.
- Robotic surgery: In recent years, robotic arms are being used in small medical surgeries, and in the future, they will be used in more complex surgeries that require pinpoint precision.
- Harvesting and Picking: We can use robots for agricultural applications like harvesting and picking. This area is suitable for automation because robots are efficient, flexible, accurate, and fast and they can improve overall production.
- Welding: High level of education and knowledge is required in the welding process, firstly robots can overcome this, secondly they increase productivity and efficiency, decrease the risk of injury so they are safer, and decrease production cost.
Types of Robotic Manipulators
There are mainly 2 main types of robotic manipulators: Serial and Parallel robotic arms.
The main difference between serial and parallel robotic manipulators is that a serial arm has its links and joints connected with each other in series to create an open loop chain while in a parallel arm; each joint is connected to both the base of the robot and the end effector.
The most famous examples of parallel manipulators are the Stewart platform and Delta robot.
Parallel Manipulators
A parallel manipulator is basically a mechanical system that uses a number of computer-controlled serial chains to support a single platform. We can use these in high accuracy, precision, and speed required applications such as simulators(e.g. flight, automobile), positioners, etc.
Definition of Delta Robots
As mentioned in the previous section, the Delta robot is an example of a parallel robot. It has three arms that are joined at the base by universal joints. The usage of parallelograms in the arms, which preserves the end effector's alignment, is the fundamental design element.
Delta robot’s design was invented by the Swiss engineer Reymond Clavel who is one of the pioneers in the development of parallel robots. Clavel wanted to design a robot that can be efficient in high-speed, low-payload operations.
Applications of Delta Robot
The main advantage of delta robots compared to traditional robotic arms is that delta robots have motors attached to the main body instead of the arms. This allows delta’s arms to move at high speed which makes the delta robot ideal for lightweight pick and place operations.
The Delta robot was first used in the packaging of chocolate pralines; now, delta robots are used in various industrial applications. Let’s talk about its strengths of it and why it is preferred in some areas. Delta Robot is not using too much space so there is no need to allocate extra space. Thanks to design, motor placement, and the lightweight arms of the robot, we have an advantage over the other robots in terms of speed. We can use our robot in production throughput, manufacturing efficiency, and quality control. They can surpass human laborers, they are faster and more consistent than humans and they don’t need breaks like them so we can have more production. Delta robots are accurate and precise in their operations. This is especially useful for assembly tasks.
The Working Method of the Delta Robot and It's Technical Specifications
Most delta robots consist of 3 servo motors that have high- torque which is mounted to a rigid frame then there is an arm that is mounted on each motor shaft; the arms must be perpendicular to the shaft’s rotational axis. To prevent twisting motion, arms are fastened to thin connecting rods organized in parallelograms. These arms are connected to a central platform. Each parallel rod has joints at both ends that are generally ball joints and allow for unrestricted movement. The end effector and various other alternatives, such as motors for extra axes of freedom, may be added to the bottom platform.
Since servo motors are mounted on the frame, the motion is translated into the arms, and because of this design; the motors need to have high- torque to counteract the increased leverage applied by the payload in the shaft.
Now, we are gonna talk about kinematics. A fundamental and well-established subject in robotics, kinematics is the study of the link between a robot's joint coordinates and its spatial organization.
For the kinematics of the delta robot, there are inverse kinematics and forward kinematics.
Inverse kinematics involves finding the appropriate angles (theta1, theta2, theta3) for each of the three arms that correspond to the desired position of the end effector (X, Y, Z).
Forward kinematics involves determining the position of the end effector (X, Y, Z) if the angles of the arms (theta1, theta2, theta3) are known.
There are different variations of delta robots according to their degree of freedom:
- There are 3- DOF Delta Robots where the end effector can move freely around X, and Y axis and has limited freedom in the Z axis which have the arms connected directly to the motors.
- 4- DOF Delta Robots which are originally invented by Clavel. The 4th axis of freedom is the theta motion around the Z axis.
- 6- axis Delta Robots which in addition to the 3-DOF Delta Robots; have 3 extra degrees of freedom thanks to the serial kinematic with 3 rotational degrees attached to the end effector.
Conclusion
Robotic manipulators have come a long way since they were first invented and they can be classified in many ways. In this blog; they were classified into serial and parallel manipulators Then Delta robot was given as an example for the latter type of manipulators.
Delta robots can be considered as a technological marvel since it introduced many advantages over serial robotic arms without creating serious disadvantages. This blog gives a brief description about this marvel that will hopefully enlighten more people about it.
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