Open sesame –

Radar-based motion detection for automatic door opening.

For several decades now, we have enjoyed the benefits of automatically controlled doors. We usually encounter them in public buildings such as department stores, banks, or supermarkets. They provide us with greater convenience and are an important measure to enable barrier-free access. We gain access to the inside or outside through our presence or movement. Contactless and unconscious. Using the sensors is practical and convenient, especially when we don’t have a hand free.

For the building itself, installing automatic doors increases energy efficiency. Doors or gates don’t remain open any longer than necessary and prevent heating bills from skyrocketing. The technological principle is also used for barrier-free access. Sensor-controlled door opening has long been part of our everyday life. But motion sensors have a few challenges to overcome.

Open and closed – with every movement

In order to trigger opening or closing, little sensors are installed that detect movements in their surroundings. The tricky thing is to avoid misinterpreting movements. In addition, the function should be as precise as possible. The automatic system should be triggered when we actually need it – i.e. only react to relevant events. It shouldn’t close or open in the event of movements by animals or passers-by. Such false triggering minimises efficiency for this use case. Also, the door or gate should only be open as long as is actually necessary. In addition, there are the influences of the measurement environment, which can impact performance. For example, components, technical systems, vehicles, or even the weather can affect functionality.

Detection & information processing

The technical challenge lies in filtering the detected information appropriately, suppressing interference factors, and programming the sensor to transmit only certain signals. The properties of the measuring method used lay the foundation for the basic function. The more extensive the data provided by each technology, the more efficient the function is.

However, as the development work and functionality increase, so do the costs of the sensor solution. By further developing the current sensor technologies, manufacturers are increasingly able to sell the products at affordable prices, despite advanced functions. Thus, some of the challenges presented by the use case of automatic doors can already be solved today.

PIR and RADAR open any door

Two means of measurement have prevailed on the market so far, thanks to their benefits: passive infrared sensors and radar detection. Both technologies are suitable for automatic door opening. However, they differ significantly in terms of their functional capabilities and associated performance. Until recently, radar was also thought of as very expensive and was mainly considered for demanding applications. At the same time, PIR was considered the best choice for low-cost, simple door opening. Meanwhile, prices have been increasingly converging. Through radar’s special properties, it boasts a price-performance ratio making the technology attractive even for the low-cost range and rendering the original rules obsolete.

More information means more efficiency

Compared to PIR, radar provides additional object information that contributes to the motion sensor’s functioning. While infrared only receives information about a movement, radar provides additional data when used as a means of positioning. Depending on its modulation, the sensor can determine not only the presence of a moving and/or stationary object, but also its speed, direction of movement, distance, and angular position. Users thus are provided with comprehensive data on the current activity in the detection area which enable the object to be positioned and observed with precision. Analysis and evaluation of the raw data during signal processing allow the radar system’s function to be precisely specified. For example, the sensor uses the directional information to detect whether a person is approaching or moving away from the door. The door might then only open when someone is approaching, for instance.

Reliable when others fail

Another plus point about radar sensors is their robustness. This owes primarily to their operating principle. The sensors utilise electromagnetic waves to detect and locate objects. The waves cannot be influenced by lighting conditions – so the technology can be employed day and night. Radar also boasts a wide operating temperature range. Cold or heat don’t affect the technology. Other environmental influences such as weather, dust, or dirt don’t impact the functionality of radar either. This makes the sensors ideal for outdoor deployment. Other sensor technologies, to the contrary, work with light, heat, or sound waves. This causes problems in the dark or extreme temperatures, or with insulating materials, vibrations, or noise.

Extensive functionality and reliability don’t constitute the essential purchase criterion for every application. Sometimes users are simply looking for a cheap solution and will put up with limitations and inaccuracy. Depending on the complexity of the task, individual considerations must be made as to which of the two sensor technologies is suitable. You can find out more about the advantages of radar equipment and radar in comparison to PIR here.

Application examples

InnoSenT GmbH has been manufacturing extremely small sensors that are successfully being used as door sensors since the company was founded. Over time, the company has launched a range of innovative products. The continuous further development of the technology is also opening new doors in the field of building automation. Customers thus now enjoy a broad selection functions to meet the challenges of their specific application. Four examples illustrate the differences between the door opener portfolios.

Use Case: automatic door at a company

    • low person traffic
    • simple motion detection sufficient
    • outdoor & indoor use
    • low power consumption

A typical example of when automatic door opening might be used is at the front door at a store or company building. Here, simple motion detection usually suffices, as relatively few people pass through the door.

The IPM-165 is ideal for this task. As a radar front end, it provides raw data, which the customer evaluates for their application using appropriate signal processing. In doing so, the customer has the option to make further adjustments to configurations in terms of sensitivity and range. Thanks to its low power consumption, the IPM-165 is also suitable for operation with solar panels.

Use Case: entry door in a shopping arcade

    • high person traffic
    • many passers-by
    • quick response & reliability
    • outdoor & indoor use

In modern shopping centres, automatic doors not only provide customers with convenience but are also an important measure for reducing energy consumption in buildings. Would-be shoppers don’t end up stuck in front of closed doors but instead are encouraged to enter by the automatic opening system. The challenge here lies in the intense person traffic entering the building. The cross-traffic passing by the shop window can confuse conventional sensors.

The SMR series from InnoSenT detects not only movement, but also the direction of movement and speed. This allows radar data to be better filtered in order to hide passers-by based on their direction of movement.

Use Case: door opening in warehouses

    • time-optimised door opening as required
    • air-conditioned facilities
    • delimitation of the coverage area
    • self-driving transport vehicles
    • quick response & reliability
    • cross-traffic

Correct and optimally coordinated opening and closing is of particular importance in many applications. One such example is gates in warehouses. Timing is often decisive here, because they must not be open for any longer than necessary, in order to prevent unauthorised persons or small animals from entering. For this purpose, the opening of the door is precisely timed according to a moving person or a self-driving vehicle.

In addition to the direction and direction of movement, the sensor also requires distance and speed information to achieve this, thus allowing the ETA (estimated time of arrival) value to be outputted. InnoSenT’s IMD-2000 boasts these features and thus also handles even more demanding tasks than motion detectors.

Use Case: turnstile & access barrier

    • access control
    • detection of objects & persons, e.g. shopping cart
    • easy detection of presence & motion

An exceptional case in the area of door sensors is what are referred to as access controls. For this purpose, turnstiles, gates, or small barriers are used, controlling access to a room. We encounter these sensors in everyday life, for example in the supermarket. They separate customers with shopping carts. The same technology is usually considered such access controls as for automatic doors.

Due to its different installation options (vertical or horizontal), the IMD-2000 ideally covers the application area of admission control.

If you have any further questions about the InnoSenT product portfolio, feel free to contact our sales team or visit the company website at: www.innosent.de/en/

picture: © MyCreative by adobe stock

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