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How to understand the terms in the specifications of the telepresence robots
Bandwidth required and Video Resolution
The required bandwidth (bitrate) of the Internet channel depends primarily on the resolution of the video image, the method of video compression, the frame rate (at 10 frames per second, the discontinuity of the video is no longer noticeable to the eye). The required bandwidth can be defined very roughly like this (see this link for details ):
[required bitrate] = [image width] x [image height] x [frame rate] x [motion rank] x 0.07
where the rank of the movement depends on how quickly the video scene changes. For example, for a still image, this value is 1, and for a Boxing scene, it is 4. If you are using a 1280x720 camera with a frame rate of 10 frames per second, you will get from formulae above
1280 x 720 x 24 x 2 x 0,07 = 3 Mbps
If the movement in the frame is fast, the rank of the movement will be 4, and you will need 6 Mbps instead of 3 Mbps.
This estimate is very approximate because it does not take into account the bit depth of color encoding, the encoding method, the number of B-frames in the video stream.
Really still scenes always require a small bandwidth, sharply changing scenes - a large band. Therefore, during the movement of the telepresence robot, when the image bounces, the image quality drops sharply, as the bit rate increases dramatically and there is not enough bandwidth to transmit the image in the same quality.
From a practical point of view, the required bandwidth does not depend on the type of telepresence robot, since all developers use the same video compression technologies (h.264 or VP8, VP9) and transmit over the same Internet network. The required bandwidth does not depend on the quality of the server, because only the P2P channel that bypasses the server is used for video transmission. Only in extremely rare cases, a TURN server is used, on which the total bandwidth of the video transmission channel depends.
Some countries have very bad internet infrastructure and the quality of the Internet as a whole and this will influence to quality of video.
The bandwidth required depends only on what video resolution you need. If the resolution of 640x480 is enough for you, you can use a channel with a bandwidth from 3 to 6 Mbps. However, if you use a 12 Megapixel camera in the same telepresence robot, then the frame size increases by about 40 times and you will already need an Internet channel bandwidth of not 3...5 Mbps, and 120 to 240 Mbps.
Aspect Ratio for Video
Monitors and video camera matrix are never square. Standard aspect ratios are 4:3, 3:2, 16:9, 17:9, etc. Therefore, in order for the image from the camera to fit completely on the monitor screen, the aspect ratios must be consistent. Look at the pictures below.
First case: tablet in robot is positioned vertically
Second case: tablet in robot is positioned horizontally
Many telepresence robots use lithium-ion and lithium-polymer batteries. They have a large capacity per unit weight. However, such batteries and robots containing such batteries are dangerous goods and are prohibited for transportation by aircraft for this reason. There are cases where they simply ignite, see for example, the table on the website of the US Department of Transportation.
The BotEyes robot uses safe lead-acid non-spillable batteries, which are safe products.
The second advantage of lead-acid batteries is their weight, which provides the robot with good stability.
To ensure the comfort of communication with the telepresence robot, it must have the height of an average person. However, from purely geometric reasons, it follows that if one of the wheels hits a bump on the floor and rises, the "head " of the robot will deviate much more. For example, if the distance between wheels is 20 centimeters and the height of the robot is 140 centimeters (140/20 = 7), under irregularities on the floor of 2 mm deviations from the vertical position will be equal 2 * 7 = 1.4 centimeters, that is very big. To resolve this problem is extremely difficult and therefore all without exception telepresence robots "shake their heads" while driving, but to varying degrees. The wider the base and lower the robot, the less amplitude of rocking.
Telepresence Robot stability. Weight and base dimensions. Segway type.
Any consumer wants to have a light robot, but the higher the robot and the lighter its base, the easier to tip it to the floor. For example, while driving, the robot can catch the body on the edge of the table and topple over. Remember: all floor lamps in the house have a heavy and wide base. The same goes for the robot. Its base should be heavy and wide to increase stability.
Stability in the direction of movement of the robot can also be provided by an automatic control system, as is done in segways. However, the disadvantage of this design is the fact that the feedback in the automatic balance system is broken as soon as the wheel hits an obstacle (for example, clings to a wall or the edge of a table) and the segway falls to the ground. Second disadvantage is autobalancing system consume energy even if they do not move.
The vast majority of video communication tools do not have a mode when you can call and at the other end of the wire will automatically "pick up". This is done to ensure privacy. However, for telepresence robots, this mode is often necessary. For example, you left the robot at home, and went to rest and want to see if the iron is turned off, whether the water flows from the tap. There is no one at home and there is no one to answer, i.e. the telepresence robot must be able to "pick up the phone" itself, i.e. automatically answer an incoming call. Similarly, if you are a remote worker and want to communicate with someone in the office, the robot should be able to automatically start a video broadcast so that you understand where to go.
The duration of operation without recharging is a very uncertain parameter that can mislead the buyer. The fact is that the main part of the energy the telepresence robot consumes while driving, i.e. it would be correct to divide this parameter into two: for the time of continuous driving and the time of work at rest. However, in real operating conditions, the robot does not travel much, most of the time is used for video communication. Therefore, unless otherwise specified, the parameter "Run time" would be logical to understand the duration of video communication without recharging.
If the telepresence robot comes without a tablet, there may or may not be an option of auto-charging for the tablet. Automatic charging means you don't need to connect the robot to the charger every time if the power level is too low. It is enough to connect the tablet charging cord to the robot only once when you mount the tablet on the robot. Next, the tablet is charged from the robot's battery, and the robot is charged from the dock.
The telepresence robot can be docked manually or automatically. Manual docking means that the remote operator drives the robot to the docking station just like he drives it around the room. Auto-docking works as follows: the operator brings the robot close enough to the docking station and presses the "Docking" button. Next, the robot analyzes the shape of the dock itself with its camera and image analysis software or using infrared sensors and LEDs, and himself drives into the dock.
Not all the robots must have this feature. The fact is that all the robots in the market today do not allow a user to change moving speed during movement and to turn robot for a small angle. It makes very difficult to dock robot and therefore robots of this type need to have autodocking feature. Unlike this, if robot allows user to change speed and moving direction accurately, like BotEyes does, then autodocking becomes unnecessary and user can dock robot using web interface very easily, see video below:
As a rule, robots with precise control and a good overview of the environment easily avoid collisions with obstacles such as chairs, tables, walls or people. However, to increase the degree of safety, some robots are equipped with automatic systems that stop the robot if the distance for obstacle becomes too small and inform the operator. This feature is called "collision avoidance".
This is done using ultrasonic distance sensors or laser rangefinders.
Telepresence robots come with fixed cameras and screens and with tilt-abled ones. The tilting head of the robot gives a greater advantage: when communicating with a person, this function allows you to point the camera directly at the face, so that both people who have entered into communication can see each other well. If the robot is used to inspect the room, the rotary camera allows you to see well and what lies on the floor and what hangs on the ceiling.
Moreover, the tilting head allows you to very accurately go around obstacles, because to see them very sharply it is enough to slightly tilt the camera down.
Telepresence robots that do not have the function of tilting the head are forced to use two cameras: one to "look down" and the second to look forward. The second camera is usually used with lenses that, however, distort the surrounding space, reduce the number of pixels of the image per unit length of the scene, or require increased bandwidth of the Internet channel (see Bandwidth required and Video Resolution above). Moreover, camera pointed at the wheels takes a useful place on the screen when the robot is not moving.
Only some robots allow you to use any gadget with any operating system (Android, iOS, Windows, MacOS) in the head of the robot or for robot control. This circumstance is very important if you have your favorite OS, your favorite browser or your favorite gadget. Providing such versatility requires additional efforts from the robot manufacturer.
If the robot uses an ordinary tablet, the power of its speakers usually does not exceed 1 watt. This is enough to communicate in a quiet room, but in a large noisy room this power is not enough and therefore some telepresence robots use external speakers to increase the volume of sound. If these speakers are missed in the robot, the user can always buy inexpensive external speakers and connect them to the tablet in the robot head robot via BlueTooth or wire through the 3.5 mm Jack connector.
Is it possible to watch the image from the robot on the TV?
Yes, you can. Many modern TVs have Skype preinstalled. Therefore, if you use a robot that can work with Skype (such a possibility is available, for example, in BotEyes robot), then you call on Skype from the TV to the robot, and control the robot from your gadget or computer.
The second option is to output the image from your gadget to the TV screen, which can be done with a WiFi or HDMI cable.
Robot speed control
Only a small number of robots on the market allow you to adjust the speed smoothly and even rarer robots allow you to smoothly change the direction of movement without stopping. In the BotEyes robot, this possibility is realized thanks to a two-dimensional control circle, the position of the cursor or finger on which immediately sets the direction and speed, which can change during movement.