JAN 2, 2019 – Authored by Aeron Systems and reprinted with permission (originally posted on www.aeronsystems.com DEC 11, 2018)
Inertial Navigation Systems For Mobile Robots
Inertial Navigation System For Mobile robots or autonomous mobile robots are being increasingly used for domestic as well as industrial and other applications. Autonomous Mobile robots are the robots which move from one place to other in order to accomplish a given task. As it is quite intuitive, such robots will certainly need navigational assistance to travel from one point to the other. Along with the navigation, we also need a system for the localization of the robot as the navigation command will depend on where the robot is located in the first place.
As robots and their use become widespread, low cost yet highly precise localization and navigation systems are required for the robots. Before we actually have a look at different technics.
A. Let Us First Understand The Ideal Navigation System For Robots
- Low cost: Since robots are set to become a commonly available resource, they will be produced in large quantities. To facilitate large-scale production, the INS that is used should be low cost. The costly navigation system will take the cost of robots high.
- Compact: Since the robots should be highly space efficient, the navigation system itself will have to be very compact.
- Secure: As the number of robots increases, their security will be a key concern. A widespread hacking attack on robots is not a remote possibility. To eliminate these attempts, the navigation system will have to be hack-proof.
- Accurate: Since robots operate in a small environment and will be dealing with picking, moving objects and other similar actions, the required accuracy is very high.
1. Following Are The Multiple Options Or Systems Available For Providing Navigational Assistance To The Mobile Robots
- Inertial Navigation Systems: Inertial navigation systems comprise of Gyroscope and accelerometers which determine acceleration in a given direction. The acceleration is double integrated to calculate the distance traveled by the robot in a given direction which is used to calculate the end location. A large variety is available as far as inertial navigation systems are concerned. Various technologies can be used to manufacture INS. Use of FOG (Fibre Optic Gyro) or RLG (Ring Laser Gyro) technologies results in highly accurate INS with minimum error. On the other hand, these systems are very costly to manufacture and large in size. This makes these systems unfit for the robotics application. The third technology available for manufacturing inertial navigation systems is MEMS – Micro Electro Mechanical Systems. MEMS technology helps in producing low-cost compact inertial navigation systems but lacks the required precision and accuracy. The output of these systems drifts away as the induced error increases over time.
- GPS/GNSS: While GPS or GNSS is one more option for robot navigation, it certainly has more limitations than advantages. First of all, the accuracy and positional accuracy of these systems is questionable. At the same time, availability of GPS signal in indoors is highly unreliable. One more major concern about GPS/GNSS is its susceptibility to getting hacked or manipulated. Since this is a major safety concern, as more awareness develops about these systems, the preference for this mode of navigation will go down.
- Camera-Based Localisation Systems: Another possible mode of communication is the use of a camera which determines the position of the robot in the room/given space and that data is processed to generate navigational commands. This systems also make use of lights, ceiling fixtures, tile design etc. to compute the exact location of the robot. These systems are still in nascent stage and will need some time to mature.
- INS-GPS/GNSS Hybrid System: Another possible solution for autonomous mobile robots navigation is a hybrid system of MEMS inertial navigation systems and INS-GPS. These systems primarily depend on a MEMS inertial navigation systems for localization and navigational assistance. As well all have seen earlier, the output of these systems tends to drift away as the induced errors increase. The GPS signal can be used periodically to nil out this error and get precise locations. One more point worth considering is the evolution of MEMS INS. Though MEMS inertial navigation Systems were once upon a time known for lack of accuracy, the progress in the filtering algorithms has increased the reliability of these systems considerably.
B. This Hybrid System Comprising Of MEMS Ins And GNSS Has a Large Number Of Advantages Over The Other Systems Discussed?
- Low Cost: These systems are highly affordable. This makes them highly suitable for mass-scale production and use.
- Secure: Since these systems primarily use an independent inertial navigation system, and rely on GNSS signal only on correction, they are much more secure than only GPS/GNSS based systems.
- Accuracy Of The Output: The accuracy of the output of these systems is far better than standalone GPS/GNSS systems. One point to note is, due to advances in algorithms and filtering technics, one can get accuracy and precision comparable with RLG and FOG systems from MEMS systems.
Here Is a Table Which Compares All These Technics On Various Performance Parameters:
The above table makes it very clear that for an application like autonomous robots, MEMS-GPS/GNSS hybrid systems are the best available option.
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