Motion Controls Robotics

There are some motion control techniques in robots. Below are the explanations of motion controls:

1. Velocity Control.
It is a common control mechanism to control the velocity of a motor. The most problem in the velocity control is how to measure very low velocities. Various approaches can be used to counter this problem they are a variable measuring period or measuring the period between counts.

2. Position Control
Position control loops are very much like the traditional R/C servos: you input a desired position and the servo logic drives the output shaft to that position with whatever force is required. With position profiling the forward velocity of the robot can be any arbitrary low amount. It might be that the motor shafts advance only every so often, but they will advance smoothly and the robot will crawl along.

3. Servo Feedback Control
A servo is simply a mechanism that slaves some sort of action to some sort of input. When talking about mechanical systems, typically some sort of input motion or signal is used to control the output motion of the system using some sort of feedback to maintain the output at a level selected by the input.

4. DC Motors
Small DC motors are easy to model and control. Fortunately for us, they can be reduced to simple terms so our control algorithms are easy to code. The permanent magnet DC motor can be modeled as a device that produces torque proportional to the current flowing through it. It also produced a voltage proportional to the rotational velocity.

Types of Robots in Manufacturing

According to ISO 8373 Industrial robot is defined as an automatically controlled, reprogrammable, multipurpose manipulator programmable in three or more axes, which may be either fixed in place or mobile for use in industrial automation applications. Industrial robot is fixed robotic arms and manipulators usually used for production and transferring of goods.

There are a number of factors that will determine the type of robot is suited to your needs. These factors are determined by the factors including the axes of movement, the type of drive that is included in the robot, the speed of axis, the sensitivity of the work environment where the robot will be used, the type and shape of the work envelope, the load capability, and the structural rigidity of the robot.

Each type of application will require performance capability from the robot that will match up to the task. There are four main applications of the robot namely, The transfer and manipulation of parts, pick and place activities, spot and arc welding, and clamping for machining.

Here some examples of application robots in industry:
• Car production, robots are mostly dominated in automotive industry.
• Packaging, industrial robot are also used extensively for palletizing and packaging of manufactured goods.
• Electronic, Mass-produced printed circuit boards (PCBs) are almost exclusively manufactured by pick-and-place robots.
• etc.

Robots and Manufacturing Automation

Since the last few decades, the role of robots in industry or daily life is increasing. Almost all of high-tech industrial are assisted by a robot. Various forms of robots were created to assist or facilitate human activity. But robots do not imagine is shaped like a robot in the movie. Many industrial robots look just like a mechanical arm. Or a household robot to clean the floor, that looks just like a disc.

More sophisticated and dangerous jobs in an industry the use of robotic tools are inevitable. For example, robotic welding in the automobile industry, robots to locate and destroy landmines, robots in underground mining or oil drilling, as well as robots that work to handle toxic and hazardous chemicals. Scientists say that the varieties of intelligent robots are created to make certain jobs become more human.

It is ironic. It will urge the use of robots for human employment. On the other hand, the utilization of robots is making the work becomes more humane. For example, in car factories since last few decades, more and more welding robot is used to replace humans. As disclosed by Hubert Grosser, head of Public Relations of the Fraunhofer Institute for production engineering and automation in Stuttgart, the car body welding work is not considered humane. Technicians only monotonous and routine work, welding body parts, a complete car body. Every year more intelligent robots developed.

Mechanical Design of Robots

The design of mobile robots capable of intelligent motion and action without requiring either a guide to follow or a teleoperator control involves the integration of many different bodies of knowledge. This makes mobile robotics a challenge worthwhile. To solve locomotion problems the mobile roboticist must understand mechanisms and kinematics, dynamics and control theory.

To create robust perceptual systems, the mobile roboticist must leverage the field of signal analysis and specialized bodies of knowledge such as computer visions to properly employ a multitude of sensors technologies.

The mechanical designs of mobile robots are including:
1. Robot’s Leg. They are the most important assemblies of the mechanical platform.
2. Bearings. The most important bearing in the leg is the bearing over part X. This bearing is actually a double row angular contact ball bearings, but takes up less axial space.
3. Motors. Motors divided into 2 types. They are Drive Motor and Steer Motor. Drive motor must able to drive the wheels and produce motion in that way. And for Steer Motor divided again into two types, they are stepper motor and servo motor.
4. Frame is the mechanical platform of robot. This frame is structure to hold all parts together.
5. Transmission. The rest is transmission mechanism. It can be rotary motion by chains. And the other possibilities are using belts or gears.

Servo Motors for Robots

Servo motor is DC motor with built in gearing and feedback control loop circuitry. Servo motors are commonly using to build robot, RC plane and RC boat builders. Mostly the servo motors can rotate about 90 to 180 degrees. Even some of them can also rotate to full 360 degrees. But servo motors can not continually rotate.

Because of the capability of the servo motors it is ideally able to build robots arm and legs, rack and pinion steering. Since servos are fully self contained, the velocity and angle control loops are very easy to implement, while prices remain very affordable.

The example of simple servo motors is commonly use in radio, tape recorder etc. If you take a normal DC that usually installed at Radio Shack it has one coil with 2 wires. If you connect it to the battery then the motor will spin. If you reverse the polarity then the motor will reverse the direction. Attach the motor to the wheel of robots you will see the robot starts to move.

In a DC motor, the speed and current draw is an affected by the load. For applications that the exact position of the motor must be known, a feedback device like an encoder must be used.
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