Seth Allen of manager of Adept MobileRobots project thinks, it is as dry as a chip, dirty, dangerous that ground robot system often must handle ” the job of ” . Those who change character, it is exorbitant, dangerous that robot system is used at artificial intervening cost normally too big or the task with too low efficiency. Below a lot of circumstances, the own work ability of robot platform is a very main character, pass the motion that navigation system will monitor and control robot moves to leave one position from a position namely. The precision when running the position and campaign is the crucial factor that realizes efficient and own work, system of cable of MEMS(personal computer) gyroscope can offer feedback to detect mechanism, very useful to optimizing navigation system function.

 

 

Graph 1 in the own system that shows Seekur robot system uses advanced MEMS parts of an apparatus to improve navigation performance namely.

 

Graph 1. The Seekur system of Adept MobileRobots company.

 

# robot navigation is summarized

 

The shift of the robot is from administrative robot the central processor of overall job plan gives out what when positional change requests, begin normally. Navigation system plans through making the journey or orbit requests with beginning to carry out the position to change. The journey plans to need to consider position of usable method, foregone obstacle, robot ability and any relevant tasks target. (for example, transmissive to the specimen in the hospital robot, transmissive time is very crucial. ) the journey plans the controller that be entered by make a present of, so that undertake navigation is controlled,latter makes transmission and directional configuration file. These configuration files can plan to carry out movement and process according to the journey. This motion undertakes monitoring by a certain number of testing system normally, each testing system all generates feedback signal; Feedback controller constitutes signal and changeover becomes the journey plan after updating and condition. Graph the 2 basic block diagram that are average navigation system.

 

Graph 2. Block diagram of average navigation system.

 

The crucial measure that develops navigation system only then at understanding every kinds of function adequately, need to take its job target and limitation seriously especially. Each function has a few to be limitted clearly normally and the element that carries out easily, but the has challenge sex restriction that also can put forward a few need to try to handle. Below certain circumstance, this may be a process that explores repeatedly, identify namely and can bring again optimize good luck newly. Can be clear about a specification through an example this one process.

 

Robot of # Adept MobileRobots Seekur

 

Adept MobileRobots Seekur2 is one uses inertial navigation system (the own robot of INS) , refer to a graph 3. This car has transmission system 4 rounds, every wheel all has independence to change direction to control capacity with speed, can go up in any horizontal way neatly floating platform. This ability delivers the goods to storehouse specimen of system, hospital / recruit is transmissive the robot car in the burgeoning application such as system and legionary reinforce system is very useful.

 

Graph 3. Navigation system of Adept MobileRobots Seekur.

 

to control

 

Robot noumenon commands, namely main error signal, plan on behalf of orbit implement the journey plan that offerred journey plan and feedback testing system offer updates the difference between information. These signal are entered by make a present of converse kinematic system, latter commands robot noumenon to changeover becomes every wheel change direction to configure a file with speed. These configuration files use Akeman to turn to a relation, have consideration, integrated area of surface contact of tire diameter, watch, span and character of other and important geometry. Use Akeman to turn to principle and relation, afore-mentioned robot platform can found what link with electronic means to change angle to configuration file, the mechanical gear that in be similar to a lot of cars to turn to a system, uses – rack system. Because these relations are together with long-range means conformity, do not need to link axle with mechanical means, conduce to the oldest rate reducing consequently grind and tire slippage, reduce tire to wear away with energy loss, achieve the exercise that simple mechanical link cannot complete.

 

Wheel drive and turn to a system

 

Every wheel all has axis of a drive, with mechanical means through gear-box join comes drive is motor, through another gear-box coupling reachs optical coder in the meantime, measure the input end of Cheng feedback system namely. Turn to an axis to reach axle coupling another servo is motor, of wheel of this motor and responsible establish turn to angle. Turn to an axis to still will come through gear-box coupling the 2nd optical coder, also measure the another input end of Cheng feedback system namely.

 

Feedback detects and control

 

Navigation system uses a buildup Kalman Filter3, come through combining the data of many sensor the attitude of the robot on estimation journey graph. The data measuring Cheng on Seekur is mixed from wheel drawing turn to coder (offer changeover) with MEMS gyroscope (offer rotate) obtain.

 

Measure Cheng

 

Consumed of interest of system of the feedback that measure Cheng learns coder to be mixed to drive turn to what the axis rotates to measure a result to come the position of estimation robot, sail to with speed. In optical coder, hold back inner light source with a disc, perhaps let illuminant illuminate be on smooth sensor through thousands of tiny window. When disc rotates, can produce a series of report pulse, these pulse are entered by make a present of normally tally circuit. Every rotate the computation frequency of circuit is equal to the groovy opening number inside disc, can rotate from the pulse computation computation of coder circuit accordingly several (include fraction) . Graph 4 offerred rotate drive axis displacement of sex of computation changeover thread (the position) metabolic graph consults and concern.

 

Graph 4. Displacement of the linear that measure Cheng concerns.

 

The drive axis of every wheel and turn to axial coder to measure a result to be in turning to formula to undertake assorted with Akeman to the middle of kinematic processor, arise thereby sail to, deflexion rate, position and linear velocity measure data.

 

This advantage that surveys a system is detecting at its the function is mixed with drive directly change control to systematic photograph union, because this can be informed drive and the condition that change control to the system accurately. Nevertheless, unless can consult a group of actual coordinate, should measure a system to be in otherwise car is practical the precision of speed and directional respect is finite. Main limitation (or error source) depend on consistency of tire geometry appearance (graph 4 in the precision of D and wave motion) , and the contact between tire and ground is interrupted. Tire geometry appearance depends on crown consistency, embryo pressing, temperature, weight and all condition that produce change possibly in normal robot use process. Tire slippage depends on deflexion radius, speed and exterior consistency.

 

The position detects

 

Seekur system uses a variety of distance sensor. To indoor applying, this system uses 270° laser scanner to build map to pursue for its environment compose. Laser system returns mode and signal release time to measure object appearance, dimension and the interval with laser source through energy. In map mode, laser system passes the scanning result the many different positions inside working area to combine, descriptive work area is characteristic (graph 5) . Produced the map of object position, dimension and appearance to pursue so, as the reference that when moving, scans. When laser scanner function combines map information to use, can provide accurate positional information. If this function is used alone, meeting existence is restricted certainly, the need when including to scan stops machine and cannot handle environmental change to wait a moment. In storehouse environment, personnel, forklift, tray carries a car to reach a lot of other objects to often can change the position, this may affect the rate that reachs destination, and the precision that reachs right destination.

 

Graph 5. Laser map.

 

To the application outdoor, system of location of Seekur use whole world (GPS) undertakes the position is measured (graph 6) . The radio signal that the whole world locates the system carries at least 4 satellites transmits time to the earth apparently position undertakes triangulation, precision can amount to ±1 M less than. Nevertheless, these systems are satisfied hard without the demand that resist, the likelihood suffers building, arboreous, bridge, channel and the object effect of a lot of other types. Below certain circumstance, position of the object outdoor and character are foregone (” ) of ” city gorge, move in GPS radar harmony accept also can be used to assist when interrupting undertake positional estimation. Even if is such, when be put in dynamic condition, the car is passed or be in for example construction, the effect often can be affected.

 

Graph 6. GPS position detects.

 

MEMS horn rate detects

 

The MEMS gyroscope that Seekur system uses can measure Seekur directly about crab (perpendicular) rate of rotate speed coming back, this axis is inside department of coordinate of Seekur navigation reference as perpendicular as earthly surface. Use at computation to sail relatively to mathematical relation is fixed time inside (the simple integral that T1 measures an outcome to T2) horn rate.

 

 

One of main advantages of this method are the gyroscope that join wears to robot machine the virtual campaign of measurable car, and need not rely on gear comparing, gear appearance of geometry of unoccupied place, tire or exterior contact integrality. Nevertheless, sail to estimation need relies on sensor precision, and this precision depends on slant the crucial parameter such as buy error, noise, stability and sensitivity. Fixed slant buy error changeover is sail to drift rate, if include,slant the following relation of buy error ωBE is shown:

 

 

Slant buy error can divide it is two kinds: Condition of current sum of errors is relevant error. Seekur system is estimated be when moving slant currently buy error. Computer of this requirement navigation can identify did not carry out condition of positional change jussive, go to the lavatory to slant according to collecting into linage even at the same time buy estimation and corrective coefficient are newer. The precision of this process depends on sensor noise and can be used at collecting data and compose builds an error estimated time. If the graph is shown 7 times, allan variance curve was offerred slant buy precision and beg all be worth the handy relation between time, decided the relation of ADIS16265 then. ADIS16265 is the ISensor with the similar gyroscope that system of paragraph and one Seekur uses at present®MEMS parts of an apparatus. In this exemple, seekur but 20 seconds inside slant on average buy error is reduced to 0.01°/ second the following, beg inside the cycle that can make an appointment with 100 seconds through be in all be worth will optimize estimation result.

 

Graph 7. Curve of ADIS16265 Allan variance.

 

4 relation still conduce to Allan variance understanding (of optimal and integral time deepτ= T2–T1) . This on-line nadir is decided to be normally buy stability slants in moving. Through installing integral time τ , make its are equal to the integral time related to the nadir on the Allan variance curve that uses gyroscope, can optimize sail to estimation result.

 

Include to slant buy temperature coefficient inside the error can affect performance related the condition, accordingly they can decide to need what how long every other stops a robot to move, slant in order to update its buy is corrective. Use beforehand the sensor of calibration conduces to solve the commonnest error cause, for example temperature and power source change. For example, ADIS16060 instead beforehand the ADIS16265 of calibration may increase dimension, price and power, but can will raise 18 times relative to the stability at temperature. Change to 2°C temperature, of ADIS16060 the biggest slant buy is 0.22°/ second, and ADIS16265 has 0.012° second only.

 

If what the following relation shows sensitivity error source and sail actually become direct ratio to change:

 

 

The rated sensitivity error that business uses MEMS sensor comes in ±5% normally ±20% above, because this need undertakes calibration in order to reduce these errors. For example ADIS16265 and ADIS16135 beforehand the rated error of calibration MEMS5 gyroscope is less than ±1% , can achieve even in controlled environment more high-powered.

 

# uses model:

 

Storehouse inventory delivers the goods

 

Storehouse automation system uses forklift and data of shift of conveyer belt system at present, satisfy requirement in order to manage inventory. Forklift needs direct manual control, and conveyer belt system needs to be safeguarded regularly. For the biggest change storehouse value, a lot of storehouse are undertaking be configuringed afresh, the application that is own robot platform thereby opened wide a gate. A group of robots need to change only software, right robot navigation system undertakes retraining can get used to new job, do not need completely to carry out many engineering work to transform forklift and conveyer belt system. The crucial performance demand in storehouse delivery system is a robot must the consistency that can maintain journey pattern, can be below the dynamic environment that has fraise shift movement of safe executive motor-driven, and make sure personnel is safe. Be opposite to explain in this kind of application MEMS gyroscope feedbacks the value of Seekur, adept MobileRobots was revealed respectively with experimental means using (graph 8) and use (graph 9) below the circumstance that MEMS gyroscope feedbacks, seekur retains the ability that repeats method. Should notice, to study the effect that MEMS gyroscope feedbacks, this experiment did not use GPS or laser scans corrective.

 

Graph 8. Did not use the Seekur method precision when MEMS gyroscope feedbacks.

 

Graph 9. The Seekur method precision when use MEMS gyroscope feedbacks.

 

Pursue quite 8 with the graph 9 medium method contrail, see very easily both in the difference that preserves method precision to go up. Should notice, what use in these experiments is inchoate MEMS technology, support the stability of ~0.02°/ second. Current gyroscope issues function to be able to rise in identical cost, dimension and power level 2 to 4 times. As the continuance of this one trend, in repeat the ability that accurate navigation maintains on method to will continue to improve, this will be development more market and application (for example hospital specimen / recruit is transmissive) bring opportunity.

 

Recruit convoy

 

At present advanced research plans American national defence bureau (DARPA) still emphasizes using robot technology morely to promote military strength in draft resolution. Recruit convoy is an example of this kind of application, right now martial convoy team is exposed under hostile menace, must press the mode that can forecast at the same time slow shift. Accurate navigation lets a robot (like Seekur) more responsibility can be assumed in recruit convoy respect, the safety of the personnel in reducing way is minatory. Index of a crucial function is the administrative ability that breaks a case to GPS, right now MEMS gyroscope sails to feedback particularly useful. Technology of newest Seekur navigation is aimed at this one environment just about and develop, its use MEMS is inertial measure unit (IMUs)6 raised precision, and can accept the new technology positive result of landform management and other function domain ceaselessly in future.

 

The position performance when be being used to test this system and using IMU, undertook record and analysis to error of the method outdoor. Graph 10 compared the photograph when using the method that measure Cheng only to true path (come from GPS) error and in Kaerman the union inside filter uses the error when the law that measure Cheng and IMU. Latter positional precision is nearly 15 times former.

 

Graph 10. Use the method that measure Cheng / IMU (green) with use the method that measure Cheng only (blue) Seekur position error.

 

# conclusion

 

Robot platform develops personnel discovery, MEMS gyroscope technology provided the means with efficient economy to improve estimation of navigation system direction and overall precision. Beforehand the systematic be in order of calibration parts of an apparatus makes simple function compositive be able to come true, be helpful for developing the job to start smoothly, let an engineer can center energy to begin a system to optimize. Improve gyroscope noise, stability and precision index continuously as MEMS technology, precision and control level will rise ceaselessly, can continue to extend new market for own robot platform thereby. The MEMS IMU/6 freedom that next generation development works of the system such as such as Seekur can transfer to be become to complete collection from gyroscope is spent (6DoF) sensor. Although face the method of crab very useful, but the world is not plane after all; A lot of other application that reach future at present all can use MEMS IMU to undertake landform management and farther precision improve, aim completely through 3 gyroscope implementation feedback and corrective.