Tag Archives: Automation

Robotics and Motion Control

Across the industrial space, automation is a growing trend in factory floors throughout the world. This is essential to improve the efficiency and production rates. When creating the automated factory, engineers may introduce a robotic system or implement a motion control system. Although both can essentially accomplish the same task, they have their own unique setups, motion flexibility, programming options, and economic benefits.

The Basics

A straightforward concept, motion control initiates and controls the movement of a load, thereby performing work. A motion control system is capable of precise control of torque, position, and speed. Motion control systems are typically useful in applications involving rapid start and stop of motion, synchronization of separate elements, or positioning of a product.

Motion control systems involve the prime mover or motor, the drive, and its controller. While the controller plans the trajectory, it sends low-voltage command signals to the drive, which in turn applies the necessary voltage and current to the motor, resulting in the desired motion.

An example of a motion control system is the programmable logic controller (PLC), which is both noise-free and inexpensive. PLCs use the staple form of ladder-logic programming, but the newer models also have human-machine-interface panels. The HMI panels offer visual representations of programming the machine. With PLCs, the industry is able to control logic on machinery along with control of multiple motion-control setups.

Robots are reprogrammable, multifunctional manipulators that can move material, tools, parts, or specialized objects. They can be programmed for variable motion for the benefit of performing a variety of tasks.

Most components making up the motion control system are also a permanent part of robots. For instance, a part of the robot’s makeup includes mechanical links, actuators, and motor speed control. The robot also has a controller, which allows different parts of the robot to operate together with the help of the program code running in the controller. Most modern robots operate on HMI that use operating systems such as Linux. Typical industrial robots take many forms such as parallel picker, SCARA, spherical, cylindrical, Cartesian, or a simple articulated robotic arm.

Robot systems also make use of drives or motors to move links into designated positions. Links form the sections between joints, and robots can use pneumatic, electric, or hydraulic drives to achieve the required movement. A robot receives feedback from the environment from sensors, which collect information and transmit it to the controller.

The Differences

While the robot is an expensive arrangement, a motion control system has components that are modular, and offer greater control over cost. However, motion controller components require individual programming to operate, and that puts a greater knowledge demand on the user.

Motion control systems, being modular, offer the scope to mix and match old hardware with the new. This facilitates multiple setups, with modular configuration ability, and applicable cost constraints.

With hardware differences between products decreasing rapidly, purchasing decisions are now mostly based on the software of the system. For instance, most modern systems are plug-n-play type, and they rely more on their software for compatibility.

Use the Raspberry Pi as a PLC for Automation

If you thought the popular single board computer, the Raspberry Pi (RBPi) is suitable only for children learning to write programs in computer languages, you need to think afresh. Vytas Sinkevicius is using the RBPi as a PLC for applications in automation. Increasingly, others are also using the RBPi as a PLC replacement in automation applications.

Basically, the RBPi replaces the actual PLC, and works as the main controller. The design specifications for the RBPi PLC are:

  • 8 digital Inputs
  • 16 Analog Inputs each supporting 4-20 mA current loops
  • 4 Analog Outputs each supporting 4-20 mA current loops
  • 12 Relay Outputs for control
  • 90-264 VAC Power Supply
  • 24 VDC Power Supply (Field)
  • Real Time Clock
  • Industrial Grade Enclosure

The enclosure has an aluminum back panel with ABS sides and a clear Polycarbonate cover. The cabinet is 14 inches in width, 16 inches in height, and 7 inches in depth. Installation is simple as DIN rail mounting is followed for all modules. While the local wiring employs ribbon cables, for field wiring the center of the panel has been left wide open. The enclosure uses industrial grade terminal blocks with rising clamp screw types.

A Delta Chrome series power supply block powers the unit. The power unit accepts AC voltages from a wide range of 90 to 264 VAC, and supplies an output of 24 VDC, with several safety approvals. While the input 4-20 mA signals are from powered transmitters, all the PI-SPI-DIN modules are supplied by high efficiency switching power supplies.

A PI-SPI-DIN-RTC-RS485 module forms the heart of the system. Apart from supporting the RBPi, the module also supplies power to the RBPi via the GPIO ribbon cable. For external displays and Modbus I/O modules, there is an RS485 interface and a battery backed Real Time Clock. The PI-SPI-DIN modules also have a buffered 16-pin GPIO bus, which also carries power from the 24 VDC to the modules.

The project has software written in the C language. It emulates a gas detection system with 16 points. There are digital inputs for manual control of fans, and analog inputs for controlling fans with variable speed. The software is undergoing testing presently. It will be published after it is found to work without issues.

Although the total number of IO points is substantial, the GPIO loading on the RBPi is not very high. For instance, the SPI bus uses only three GPIO pins, since the SPI routines allow any arbitrary GPIO lines to be used for chip selects. The I2C bus uses 2 GPIO lines, while the two 4-20 mA modules use two GPIO chip selects. While the PI-SPI-DIN-8DI module uses one GPIO for chip select, the relay modules use an MCP23508 GPIO expander with 4 addresses, but uses only one GPIO chip select. Direction control takes up one GPIO pin on the RS485, while it uses GPIO UART Rx and Tx.

The entire setup of enclosure, power supply, all modules, DIN rails, and RBPi3 cost less than $600. This easily rivals any PLC on the market with the same number of IO points.

Inertial Sensing for Automation

In any type of industry, whether it is automotive, unmanned aerial vehicles, energy, logistics, agriculture, or manufacturing, automation brings increasing promises of great gains in terms of efficient utilization of resources, achieving accuracy, and safety. To achieve these gains it is necessary to identify the appropriate sensing technologies that will enhance the contextual knowledge of the equipment’s condition.

As the location or position of an equipment is a valuable input, precision inertial sensors provide accurate location information and help in maintaining accurate positioning. Where mobility is a factor, it is necessary to couple both the location and the contextual sensor information with the application. Operating in a harsh or complex environment often requires determination of position as a critical value. This is where inertial sensors help to make a difference.

Over the years, machinery has evolved from making simple passive movements, to functioning with embedded controls, and now it is moving towards fully autonomous operations, with sensors playing the enabling role. Earlier, for supporting offline analysis or process control, sensors working in isolation were adequate. However, obtaining real-time benefits requires increasingly sophisticated sensor types, while efficient processing requires important advances in sensor fusion. Therefore, increasingly intelligent sensor systems are coming up catering to complex systems on multiple platforms that require the knowledge of states the system has held in the past.

Inertial sensors used with smart machines serve two special functions, one for equipment stabilization or pointing, and other for equipment navigation or guidance. Most systems consider GPS as the most suitable for navigation. However, potential blockages cause significant concerns for many industrial systems. Some systems transition to inertial sensing when GPS is blocked, but this requires the inertial systems to be of sufficient quality to provide the same precision, as did the GPS.

Inertial sensors provide the feedback mechanism in case of servo loop or stabilization for maintaining a reliable positioning such as the antenna pointing angle, construction blade, crane platform, camera, UAV, or farming implement. For all these, the purpose is not only to provide a useful function, but also to deliver a safety mechanism or critical accuracy, even when the environment is incredibly difficult.

In reality, sensor quality matters when good performance is desired. Engineers use sensor fusion for making some correction, for instance, when correcting the temperature drift of sensors, or compensating an accelerometer when correcting for gravitational effects on a gyroscope. In such cases, this helps only in the calibration of the sensor to the environment, but does not improve the ability of the sensor to maintain performance between the calibration points. With a poor quality sensor, the accuracy falls off quickly, as the performance of the sensor rapidly drifts without expensive or extensive calibration points.

Even when using high quality sensors, some amount of calibration is desirable, especially when the aim is to extract the highest possible performance from the device. However, the most cost-effective method of calibration depends on the intricate details of the sensor, along with a deep knowledge of motion dynamics. This makes the compensation or calibration step an embedded necessity for the manufacturer of the sensor.

Automation Controller Uses Raspberry Pi Compute Module

Remote control has a new face. Based on the tiny credit card sized single board computer Raspberry Pi or RBPi, Techbase has designed a Linux-based ModBerry automation computer. They back it up with an iMod cloud platform. ModBerry is all about remote control.

This version of RBPi was introduced lately and known as the Compute Module or Computer-on-Module. People in Poland have taken up the RBPi Compute Module wholeheartedly and turned it into ModBerry. Initially, the Polish startup Sher.ly started with Sherlybox, a private cloud storage device based on the RBPi COM (Compute Module). Now, Techbase, the industrial computer manufacturer from Gdansk, Poland, has based their automation computer ModBerry 500 on the RBPi COM.

The RBPi COM is a part of the development kit that Farnell Element 14 and RS Components have released recently. The kit also contains a separate baseboard. Later plans include selling the module independently.

Techbase is already in the market with numerous Linux-ready and Linux-based automation controllers and industrial computers. Techbase supports some of its computers with its cloud-based iMod, iModCloud and iModWizard, which also provide Software-as-a-service or SaaS applications. This includes its telemetry computer iMod-X1000.

In contrast, Sherlybox is a private crowd based on local storage. With the iMod ecosystem, users can store data and control several iMod compatible computers via a cloud platform. By combining ModBerry 500 and the software from iMod, users have access to applications in the general automation market and intelligent buildings. According to Techbase, they can also monitor and control wind farms, GSM base stations and power stations. Users can set up their devices as protocol converters, telemetry modules, data loggers, servers, MODBUS routers, PLC devices, SNMP agents and many more.

The iMod system is a versatile arrangement offering multi-level, user access cloud management via configuration files. According to Techbase, its iModWizard makes it unnecessary for the user to possess any programming knowledge. Users can freely create different user profiles such as end-user, administrator and system designer. Additionally, iModCloud helps users to update software and configure services.

With iModCloud, users have custom-based actions including notifications and management, which are extremely important for remote control. Users can see the location of GPS-enabled devices on maps provided as part of data visualization capabilities. Users can access their data on smartphones or tablets. Techbase assures security via SSL certificates and encrypted VPN communication.

The ModBerry 500 operates on a wide-ranging 9-24V AC/DC supply. It is available in commercial as well as in extended models, which can work between -25 and 80°C. The physical dimensions are 106x91x61 mm. The ModBerry 500 gets its computing power from the RBPi COM, which provides it with the 700MHz ARM11 Broadcom system-on-chip processor running Raspbian Linux. The module also shares its 512MB RAM and its 4GB NAND flash storage with the ModBerry.

The hardware features of the ModBerry include several real-world ports such as a USB 2 host port, a 10/100 Ethernet port, a slot for SIM card, audio out and a user programmable button. Other ports include an HDMI port and a reset button. There is also a pair of RS-232 and RS-485 ports, CAN ports and a 1-wire bus.

For more information on ModBerry 500, refer to this website.

Gardening with the Raspberry Pi

Many of you may be garden enthusiasts and would welcome the idea of automating some of the maintenance requirements of your plants. For example, keeping tabs on the quantity of water that is required by the plants based on the moisture in the soil, the available sunlight and the environmental temperature might be easy for an experienced gardener. However, gardeners who have just started gardening find it a difficult equation to balance. Even an experienced gardener may have to depend on a novice if taking leave from his garden for a few days.

With a Raspberry Pi (RBPi), most of the above gardening issues can be fixed. The Raspberry Pi can take care of the garden’s watering requirements based on a few environmental measurements. This can bring relief to an experienced gardener forced to leave his beloved plants for a few days. The novice gardener can quit worrying if he is starving his plants or drowning them in water. This is how Devon approached the problem with his Raspberry Pi.

Avid gardening enthusiasts know that too much water to a plant can be as bad as too little. For the Raspberry Pi to determine how much water should be delivered to the plant, it is necessary to know how much moisture is present in the soil in the first place. That, combined with the temperature and the amount of available light can let Raspberry Pi control the pump that delivers the water to the garden.

Since Raspberry Pi is not capable of measuring analog signals that most sensors put out, an Analog to Digital Converter attachment is necessary. For this, using the MCP3008 ADC is a good choice since it allows eight sensors to be used at a time. For sensing the amount of sunlight available, a Light Dependent Resistor or LDR is useful. To measure the ambient temperature with some amount of precision, a temperature sensor such as the TMP35 or TMP37 will do. For sensing humidity in the soil, a homemade humidity sensor using a few long metal nails will be fine.

All the sensors will need a DC voltage supply and a return ground connection, with the signal from each sensor going to one of the channels of the ADC. The 3.3VDC from the Raspberry Pi board is good enough for the sensors. While only one temperature sensor and one LDR is enough, you may need more than one humidity sensor, depending on how big your garden is.

The humidity sensors check the resistance of the soil between a pair of probes inserted into the ground. As the soil dries up, the resistance increases between the two probes of the humidity sensor. If several such probes are placed at different places in the garden, the Raspberry Pi has a fairly good idea of the state of dryness of the soil in the garden.

The final and most important part of the entire system is the pump that delivers water to the garden. Using a tank and a submersible pump eliminates a whole bunch of issues that many gardeners face. You can experiment with drip-irrigation also if you like the idea. Devon has kindly shared the software and the code used, and you can download them here.