BLDC Motor & Controller For EV

The brushless DC (BLDC) motor is becoming increasingly popular in sectors such as automotive (particularly electric vehicles (EV)), HVAC, white goods and industrial. This is because it does away with the mechanical commutator used in traditional motors, replacing it with an electronic device that improves the reliability and durability of the unit. Major advantage of a BLDC motor is that it can be made smaller and lighter than a brush type with the same power output, making the former suitable for applications where space is tight. This is made possible with the help of a BLDC motor controller unit. In this report, we will give a short description of brushless DC motor theory of operations, different methods to control a brushless DC motor and approximate BOM cost for developing a sensorless BLDC controller for controlling the BLDC motor of 1KW in EV.

Types and methods to control BLDC motor

In an electric vehicle the main electronic components that make the drive are motor, controller, harness, batteries and throttle. A MCU uses the input from position sensors or by coils back emf measurements, which indicates the position of the rotor, to energize the stator coils at the correct moment. Precise timing allows for accurate speed and torque control, as well as ensuring the motor runs at peak efficiency. Commutation ensures the proper rotor rotation of the BLDC motor, while the motor speed only depends on the amplitude of the applied voltage. The amplitude of the applied voltage is adjusted using the PWM technique. The required speed is controlled by a speed controller, which is implemented as a conventional Proportional-Integral (PI) controller. The difference between the actual and required speeds is input to the PI controller which then, based on this difference, controls the duty cycle of the PWM pulses which correspond to the voltage amplitude required to maintain the desired speed.

The major advantages of brushless DC (BLDC) motors are its low rotor inertia, fast response, high reliability and low maintenance. This is due to the result of replacing brushes/mechanical commutator with an electronic commutation controller and rotor feedback device. A BLDC motor can be of two kinds, an in runner and an out runner type, and there are two methods by which we can control a BLDC motor.

  • Sensored

  • Sensorless

Sensor method works well, but add cost, increase complexity (due the additional wiring), and reduce reliability (due in part to the sensor connectors that are prone to contamination from dirt and humidity). Sensorless control addresses these drawbacks.

In sensor mode, Brushless DC motors usually consist of three main parts: a Stator, a Rotor and Hall Sensors. For the estimation of the rotor position, the motor is equipped with three hall sensors. These hallsensors are placed every 120° in fig 1. With these sensors, 6 different commutations are possible. Phase commutation depends on hall sensor values. Power supply to the coils changes when hall sensor values change. With right synchronized commutations, the torque remains nearly constant and high. In short a BLDC motor using position sensors uses the output from the devices – controlled by a MCU and operating through a driver – to switch MOSFET or IGBT to correctly sequentially energize the coils. The transistors are triggered (and coils energized) when the Hall sensor output changes state.

The benefits to sensor-based BLDC motors include that they are able to detect the absolute rotor position allowing for the application to have a high starting torque. Also sensor-based BLDC motors do not require as much software development. Finally, sensor-based BLDC motors are the best for applications in which the torque varies greatly, easily transitioning from high to low in torque. The downsides to sensor-based BLDC brushless motors include that they have a singular point of failure; making it so that is one part of the motor fails, the entire system stop. Additionally, they have more components and, as such, there is less flexibility in their construction.

In the sensorless variant of the BLDC motor, there are no Hall-effect sensors (fig 2). Instead, as the motor rotates, the back EMF in the three coils varies in a trapezoidal waveform. In every commutation step, one phase winding is connected to positive supply voltage, one phase winding is connected to negative supply voltage and one phase is floating. The back-EMF in the floating phase will result in a “zero crossing” when it crosses the average of the positive and negative supply voltage. The zero crossing occurs right in the middle of two commutations. At constant speed, or slowly varying speed, the time period from one commutation to zero-crossing and the time period from zero-crossing to the next commutation are equal. This is used as basis for this implementation of sensorless commutation control. Unlike sensor-based BLDC motors, sensorless BLDC motors have fewer components and have greater flexibility in their construction because of the fact that they do not have sensors. One disadvantage is that no back EMF is generated when the motor is stationary, so startup is affected by operating in open loop. Consequently, the motor can take a short time to settle and run efficiently. A second disadvantage is that at low speeds the back EMF is small and difficult to measure, which can result in inefficient operation.

Conclusion

The motor power used in most EV in India is 650W to 1250W, the latest government norms allow it to be 650W, most of them run on 850W and higher, which adversely affects the battery life. The controller used is ~40A, 48V output, uses around 24 MOSFETs and powers all electric components. Infact, many of the pros to sensor-based BLDC motors become cons for sensorless BLDC motors, beginning with finding the exact rotor position. However the sensorless BLDC motors are simpler, advanced and potentially more reliable than units that use Hall-effect sensors, especially if the application is in a dirty and humid environment. The motors rely on measurement of back EMF to determine relative positions of stator and rotor so that the correct coil energizing sequence can be implemented. A good quality controller must be used to increase performance of the motor and other overheating issues. Also the controller should be installed with electrical brake cut off and vehicle body is kept light in weight in order to increase life of the battery.

Overview of Internet of things

IoT systems allow users to achieve deeper automation, analysis, and integration within a system. They improve the reach of these areas and their accuracy. IoT utilizes existing and emerging technology for sensing, networking, and robotics.IoT exploits recent advances in software, falling hardware prices, and modern attitudes towards technology.

IoT – Key Features

The most important features of IoT include artificial intelligence, connectivity, sensors, active engagement, and small device use. AI – IoT essentially makes virtually anything “smart”, meaning it enhances every aspect of life with the power of data collection, artificial intelligence algorithms, and networks. Connectivity – New enabling technologies for networking, and specifically IoT networking, mean networks are no longer exclusively tied to major providers. Networks can exist on a much smaller and cheaper scale while still being practical. IoT creates these small networks between its system devices. Sensors – IoT loses its distinction without sensors. They act as defining instruments which transform IoT from a standard passive network of devices into an active system capable of real-world integration. Active Engagement – Much of today’s interaction with connected technology happens through passive engagement. IoT introduces a new paradigm for active content, product, or service engagement. Small Devices – Devices, as predicted, have become smaller, cheaper, and more powerful over time. IoT exploits purpose-built small devices to deliver its precision, scalability, and versatility.

IoT – Advantages

Improved Customer Engagement – Current analytics suffer from blind-spots and significant flaws in accuracy; and as noted, engagement remains passive. IoT completely transforms this to achieve richer and more effective engagement with audiences. Technology Optimization – The same technologies and data which improve the customer experience also improve device use, and aid in more potent improvements to technology. IoT unlocks a world of critical functional and field data. Reduced Waste – IoT makes areas of improvement clear. Current analytics give us superficial insight, but IoT provides real-world information leading to more effective management of resources. Enhanced Data Collection – Modern data collection suffers from its limitations and its design for passive use. IoT breaks it out of those spaces, and places it exactly where humans really want to go to analyze our world. It allows an accurate picture of everything.

IoT – Disadvantages

Security – IoT creates an ecosystem of constantly connected devices communicating over networks. The system offers little control despite any security measures. This leaves users exposed to various kinds of attackers. Privacy – The sophistication of IoT provides substantial personal data in extreme detail without the user’s active participation. Complexity – Some find IoT systems complicated in terms of design, deployment, and maintenance given their use of multiple technologies and a large set of new enabling technologies. Flexibility – Many are concerned about the flexibility of an IoT system to integrate easily with another. They worry about finding themselves with several conflicting or locked systems.

Compliance – IoT, like any other technology in the realm of business, must comply with regulations. Its complexity makes the issue of compliance seem incredibly challenging when many consider standard software compliance a battle.

IoT – Hardware

The hardware utilized in IoT systems includes devices for a remote dashboard, devices for control, servers, a routing or bridge device, and sensors. These devices manage key tasks and functions such as system activation, action specifications, security, communication, and detection to support-specific goals and actions.

IoT – Sensors

The most important hardware in IoT might be its sensors. These devices consist of energy modules, power management modules, RF modules, and sensing modules. RF modules manage communications through their signal processing, WiFi, ZigBee, Bluetooth, radio transceiver, duplexer. The sensing module manages sensing through assorted active and passive measurement devices. Here is a list of some of the measurement devices used in IoT:

 IoT – Software

IoT software addresses its key areas of networking and action through platforms, embedded systems, partner systems, and middleware. These individual and master applications are responsible for data collection, device integration, real-time analytics, and application and process extension within the IoT network.

Real-Time Analytics

These applications take data or input from various devices and convert it into viable actions or clear patterns for human analysis. They analyze information based on various settings and designs in order to perform automation-related tasks or provide the data required by industry.

 IoT – Technology and Protocols

IoT primarily exploits standard protocols and networking technologies. However, the major enabling technologies and protocols of IoT are RFID, NFC, low-energy Bluetooth, low-energy wireless, low-energy radio protocols, LTE-A, and WiFi-Direct. These technologies support the specific networking functionality needed in an IoT system in contrast to a standard uniform network of common systems.

IoT – Common Uses

IoT has applications across all industries and markets. It spans user groups from those who want to reduce energy use in their home to large organizations who want to streamline their operations. It proves not just useful, but nearly critical in many industries as technology advances and we move towards the advanced automation imagined in the distant future. Engineering, Industry, and Infrastructure Applications of IoT in these areas include improving production, marketing, service delivery, and safety. IoT provides a strong means of monitoring various processes; and real transparency creates greater visibility for improvement opportunities. The deep level of control afforded by IoT allows rapid and more action on those opportunities, which include events like obvious customer needs, nonconforming product, malfunctions in equipment, problems in the distribution network, and more. IoT allows operations to remove much of the human intervention in system function, farming analysis, and monitoring. Systems detect changes to crops, soil, environment, and more.

Drones — What are drones ?

The word drone has been more commonly associated with male insects in the past, it is now better known as an unmanned aerial vehicle. This means it is an aircraft without a human pilot aboard. Although the drone originated for military operations, where missions are classed too dangerous for humans – and can often involved carrying weapons for airstrikes, civilian drones now outnumber those of the military. It has been estimated more than a million were sold by 2015. There are six categories of drone – target and decoy, reconnaissance, combat, logistics, research and development and civil and commercial.

Unmanned aerial vehicles (UAVS), also known as drones, are aircraft either controlled by ‘pilots’ from the ground or increasingly, autonomously following a pre-programmed mission. While there are dozens of different types of drones, they basically fall into two categories: those that are used for reconnaissance and surveillance purposes and those that are armed with missiles and bombs.

The use of drones has grown quickly in recent years because unlike manned aircraft they can stay aloft for many hours (Zephyr a British drone under development has just broken the world record by flying for over 82 hours nonstop); they are much cheaper than military aircraft and they are flown remotely so there is no danger to the flight crew.

As well as armed drones, the UK has several types of surveillance drones, most notably Watchkeeper, a drone jointly produced by Israeli company Ebit and Thales UK. The UK is purchasing 54 Watchkeeper drones and ground stations at a cost of £860m. The first ten will be built in Israel and then production will transfer to a specially built facility in Leicester. Testing is taking place at Aberporth in Wales and Watchkeeper is due to enter service in 2010. There have recently been reports that Watchkeeper may be armed in the future.

Serious Concern

UN’s Special Rapporteur on extrajudicial, summary or arbitrary executions, Philip Alston, has said that the use of drones is not combat as much as ‘targeted killing’. He has repeatedly tried to get the US to explain how they justifies the use of drones to target and kill individuals under international law. The US has so far refused to do so. In a report to the UN he has said the US government (and by implication the UK government) “should specify the bases for decisions to kill rather than capture particular individuals …. and should make public the number of civilians killed as a result of drone attacks, and the measures in place to prevent such casualties”.

A further question is the extent to which operators become trigger happy with remote controlled armaments, situated as they are in complete safety, distant from the conflict zone.

Increased Surveillance

Military drone manufacturers are looking for civilian uses for remote sensing drones to expand their markets and this includes the use of drones for domestic surveillance. Drones will no doubt make possible the dramatic expansion of the surveillance state. With the convergence of other technologies it may even make possible machine recognition of faces, behaviours, and the monitoring of individual conversations. The sky, so to speak, is the limit.

Aside from military missions there are thousands of civilian drones used for aerial crop surveys, photography, search and rescue operations and delivering medical supplies to inaccessible reasons, among others.

A 14-year-old in Gujarat received a Rs 5 crore Memorandum of Understanding (MoU) for the production of drones designed by him, reported the Times of India. Harshwardhan Zala on Thursday signed a deal with the Department of Science and Technology, Government of Gujarat for manufacturing drones that would be able to detect and defuse land mines on a battle field.

Speaking to The Times of India, he described the drone as a device being equipped with sensors and thermal meters along with a 21-megapixel camera for taking high resolution pictures. He said, “The drone has been equipped with infrared, RGB sensor and a thermal meter along with a 21-megapixel camera with a mechanical shutter that can take high resolution pictures as well.”

The drone can send out waves up to eight square meters while it is two feet above ground level. These waves are able to detect land mines and send their location to the authorities. “The drone also carries a bomb weighing 50 gram that can be used to destroy the landmine,” he told TOI further.

Recreational use also includes police investigations, agriculture and archaeology.

In January 2016 Ehang UAV announced drones capable of carrying passengers. While other people have found different uses for the drones – as they are sometimes used to drop items into prisons.

Companies such as Amazon have been looking into developing drones which can deliver packages to people’s homes after they order online.

China is developing a factory to build hunter-killer drones in Saudi Arabia – the first in the Middle East.

But an effective counter-issue is the collateral damage a UAV can cause if it spins out of control and crashes on human settlements. UAVs may be designed primarily for military use, but 90 per cent of Indian airspace is civilian, and restricting UAVs to military airspace could be impractical.

Aeronautical Development Establishment organized its first international conference on autonomous unmanned vehicles in 2009 (ICAUV), and again in 2011. This has been the only government organized event in India till date exclusively on unmanned systems. Unmanned Systems Association of India (USAI) has been recently formed and is completely dedicated towards all the activities and regulations pertaining to the unmanned systems industry in India.

Presently all UAV flying is done with permission from Directorate General of Civil Aviation (DGCA) and Ministry of Defence (MoD). This has been done since all the official UAV flying has been by the military and government agencies. Integrating the UAVs into civilian air space is a challenging job. Suggestions are invited to create a regulated policy for unmanned aviation and unmanned systems in India. Please contact us or become a member of USAI and join us in lobbying for regulated UAV operations in India.