IMECE ROBOTIC HIGHWAY SAFETY MARKERS

Transcription

1 Poceedings of IMECE2002 ASME Intenational Mechanical Engineeing Congess & Exposition Novembe 17 22, 2002, New Oleans, Louisiana IMECE ROBOTIC HIGHWAY SAFETY MARKERS Shane M. Faito Assistant Pofesso Depatment of Mechanical Engineeing Univesity of Nebaska Lincoln, NE Mak E. Rentschle Reseach Assistant Depatment of Mechanical Engineeing Massachusetts Institute of Technology Cambidge, MA ABSTRACT Pope taffic contol is citical in highway wok zone safety. Taffic contol devices such as signs, baicades, cones, and plastic safety baels ae often used. Accidents can occu because of impope wok zone design, impope wok zone housekeeping, and dive negligence. One solution is to automate safety devices. This pape pesents a mobile safety bael obot. The Robotic Safety Baels ae the fist elements of a team of Robotic Safety Makes (RSM) that includes signs, cones, and possibly baicades and aestos. To be pactical the system must be eliable and have a low pe obot cost. A obot that malfunctions could ente taffic and ceate a significant hazad. Also, multiple safety makes ae used and baels ae often stuck by vehicles. Safety makes with a high eplacement cost ae not pactical. This pape descibes the motivation fo the obotic safety make system and how it could impove wok zone safety. The design of thee obot pototypes is pesented. A contol achitectue is discussed that has been implemented in simulation and patially tested on the pototype obots. INTRODUCTION The safety of highway constuction and maintenance wokes is extemely impotant. Fo evey billion dollas spent on oad constuction, moe than 33 people die in accidents elated to that wok [1]. Studies have found that accidents in wok zones have inceased by 6.8% in the some states and as much as 119% in the state of Viginia [2]. The nation s highway system is aging and is in need of constant epai. Inceased maintenance and constuction will esult in moe injuies and moe fatalities unless new ways ae found to pevent these accidents. Pope taffic contol is citical to wok zone safety. Taffic contol devices such as signs, baicades, taffic cones, and plastic safety baels ae often used. Figue 1: Robotic Safety Bael One method to impove wok zone safety is to implement a smat wok zone consisting of automated devices that impove safety. This pape pesents a mobile obotic safety bael, Figue 1. Safety baels ae placed on the peiphey of the wok zone to guide taffic and to seve as a visible baie between taffic and wok cews. These baels consist of a bightly 1 Copyight 2002 by ASME

2 coloed plastic dum (appoximately 130cm high and 50cm in diamete) that is attached to a heavy base. Often, hundeds of baels ae manually placed in a typical wok zone. The Robotic Safety Bael (RSB) eplaces the heavy base of a typical safety bael with a mobile obot. The mobile obot can tanspot the safety bael and obots can wok in teams to povide taffic contol. Independent, autonomous bael motion has seveal advantages. Fist, the baels can self-deploy, eliminating the dangeous task of manually placing baels in busy taffic. Second, the bael positions can be quickly and emotely econfigued as the wok zone changes. Baels could continuously follow wok cews to maintain optimal placement fo safety. The Robotic Safety Baels ae the fist elements of a team of Robotic Safety Makes (RSM) that includes signs, cones, and possibly baicades and aestos. To be pactical the Robotic Safety Make System must be eliable and have a low pe obot cost. A obot that malfunctions could ente taffic and ceate a significant hazad. The system will be designed so citical components (softwae and hadwae) have multiple edundancy. Cost pe obot is also citical. Multiple safety makes ae used and baels ae often stuck by vehicles. The system is designed so that each individual obot is simple, eliable, and inexpensive. The poposed appoach may have a highe equipment cost than taditional systems, howeve, thee ae possible cost eductions in labo and inceased woke safety. The appoach is not fitted fo evey wok zone but thee ae many situations whee it would be useful and pactical. BACKGROUND Accidents can occu because of impope wok zone design, impope wok zone housekeeping, and dive negligence. Steps ae being taken to impove wok zone design. Many agencies now equie witten safety plans. Also, technology is being used to impove communication in wok zones, leading to bette wok contol [1]. Wok zone housekeeping may be the most impotant element in educing accidents [1]. A good safety plan is not helpful if it is not popely executed. Wok zone housekeeping involves tasks such as coveing and uncoveing signs and moving makes (baels, cones, signs) as the wok pogesses. While housekeeping is impotant, it comes at a vey high cost. Woke time is wasted setting up and teaing down hundeds of constuction zone safety devices. Safety makes often need to be deployed and etieved at the beginning and end of each wokday. Removing the makes o coveing them is time-consuming, but leaving them in open view aound the clock adds to unsafe conditions. Safety makes that ae simply moved to the side of the oad emain highly visible. The constant pesence of safety makes leads to dive complacency. In addition, deployment and etieval activities ae extemely dangeous since the constuction woke is vey close to passing motoists. In this county, the cost of congestion to motoists in lost poductivity is estimated to be appoximately $100 billion annually, not including the cost of wasted fuel and envionmental damage [3]. Passing motoists ae also patly to blame fo accidents in constuction zones. Typically, motoists only slow 10-mi/h upon enteing a wok zone [4], theefoe it is vey impotant to make the dive awae of dangeous conditions. Thee ae many ways to incease woke safety. Fo example, evey oad unde epai could be completely closed to public taffic. Anothe solution may be to simply incease the numbe of safety cones and baels in wok zones to bette channel taffic. While these solutions decease the theat of injuy, the cost of mateials, wokes time, and dive inconvenience is lage. Obviously a easonable balance must be found between woke safety, cost, and dive convenience. RELATED RESEARCH Thee is much eseach investigating smat highway systems and wok zones. A lage body of eseach exists on the Intelligent Vehicle Highway Systems (IVHS). This system uses infomation technology to povide infomation to taveles, impove taffic contol and congestion, and incease the efficiency of commecial vehicle and tansit opeations [3]. Cuent IVHS eseach does not addess taffic contol though constuction and maintenance aeas. Although thee is geat potential fo integation of IHVS and smat wok zones. Seveal pojects have applied obotic technologies to highway constuction equipment. One poject ceated a Remotely Diven Vehicle (RDV). The RDV is a adiocontolled dump tuck that is used as a shadow vehicle duing slow-moving maintenance opeations [5]. The shadow vehicle follows the wok cew to seve as a baie. The RDV emoves the dive fom being exposed to ea-end collisions while diving the shadow vehicles. Anothe highway constuction obotics eseach poject is the development of automated paving machines [6]. This system has inceased the speed of these machines as well as the quality, and the smoothness of the pavement. The Advanced Highway Maintenance and Constuction Technology (AHMCT) Reseach Cente at the Univesity of Califonia, Davis has developed seveal automated highway maintenance systems. One system is an automated lase-guided lane stiping machine [7]. This system is a taditional lanestipe-painting vehicle that uses sensos to patially automate the stipe painting pocess. A second poject ceates tetheed obots fo oadway cack sealing [8]. Nomal cack sealing is a dangeous, tedious, and slow pocess. In this system, a tetheed obot follows a wok vehicle to out pavement cacks pio to 2 Copyight 2002 by ASME

3 sealing. Othe vehicle mounted obots can then seal the cacks. A thid system is a flying aeial bidge-inspection system with a emote opeato. This system inspects difficult to access aeas on bidges using a video camea [9]. Anothe eseach goup has developed a obotic paintemoval system fo bidges. This system consists of a obot placed at the end of a long boom. The obot emoves paint while collecting debis. This pevents the emoved lead paint fom polluting the envionment [9]. Thee has been eseach in the automated placement of safety devices. A tele-obotic system has been developed to apply aised, eflective pavement makes [10]. Peviously, the makes wee applied by hand, with the woke positioned in a low-iding bay on a tuck. This pocess was vey time consuming and vey dangeous since the makes wee applied by the woke extending thei hands into oncoming taffic. Two othe systems automate the placement of safety devices with a safety cone dispense. These systems automatically and quickly deploy and emove ows of waning cones [11, 12]. The systems ae modified maintenance vehicles (pickups) that place cones as the vehicle tavels down the oad. The vehicle can then dive along the line of cones and etieve the makes. Cones can be placed on eithe side of the vehicle and at vaious distances between cones. These pojects have focused on smalle waning cones. Lage cones and baels ae often used so the wok zone is visible fom a gate distance and fom the inside of a passing vehicle. These pevious systems function in a fundamentally diffeent way than the poposed appoach. The pevious systems place makes in a seial fashion as the deployment vehicle is diven. The advantage of this appoach is that the makes themselves do not need to be modified. One "centalized" obotic system is used to deploy/etieve the makes. The cost and complexity of the oveall system is not elated to the numbe of makes deployed. The disadvantage of these systems is that the makes ae deployed seially so the time equied fo deployment is linealy elated to the numbe of makes placed. Also, the location of the makes can not be changed once they ae deployed. Theefoe the system cannot adapt to changes in the wok zone. The poposed appoach decentalizes the obotic system so the makes themselves become "smat". The advantage of this appoach is that the makes can adapt to changes in the wok zone. If a cew moves, the safety makes can follow and always maintain an optimal location. The makes can also be moved/deployed/etieved in paallel deceasing deployment time. The disadvantage of this appoach is that the cost of the oveall system linealy scales with the numbe of makes used. Both appoaches have advantages and thee ae wok zone situations whee each would incease woke safety and efficiency. The centalized appoach (a single obot that deploys numeous baels) would lend itself to situations whee many baels that ae seldom e-configued ae used. The decentalized appoach (whee each bael is a obot) would be useful in situations whee fewe baels ae used and ae often moved. Fo example, a situation might equie a wedge of baels to follow a cew that patches a pothole evey quate mile. Individual mobile bael obots could diect taffic quickly and efficiently without endangeing wokes and wasting woke effot. The obots could self-deploy, self-etieve, and self-econfigue. SYSTEM DESIGN In this poject thee pototype obotic safety baels wee designed, built and ae being tested. The objective is to demonstate the usefulness in inceasing woke safety and deceasing taffic congestion delays though a moe efficient, bette-maked wok zone Design Objectives Thee ae seveal physical equiements that a obotic safety bael must meet. The obot needs to be at least as stable as a taditional safety bael. The obot and bael need to emain stationay in 55mph winds and weigh less than 50 lbs. (so they can be moved by wokes). The pototypes must have the same footpint as taditional baels so cuent tanspot methods can be used. The device needs to cause minimal damage to vehicles if an impact occus. It is impotant that the obots do not become a safety hazad. The obot needs to climb slopes up to 7% gade and tavel at 5mph (the speed of some maintenance opeations such as stiping). The obot needs to tavese obstuctions, bumps, and depessions. The obot needs to opeate in inclement weathe. The obot also needs to maneuve within the wok zone. Thee ae two systems-level design equiements that need to be addessed if the obot baels ae to be successful: 1) high eliability and 2) low cost. The system must be vey eliable in hadwae and softwae. A obot that malfunctions could ente into taffic and ceate a significant hazad. The system should be designed so citical components have multiple edundancy. The multi-obot aspect of the appoach will be utilized to incease eliability-all obots could monito thei neighbos. Also, an encoded Radio Fequency (RF) caie wave will be boadcast in the local aea so all obots could be stopped in an emegency. Thee is extensive wok in fault toleant engineeing. Robots ae now being used in citical opeations such as sugey and many systems with human inteaction. All eliability issues wee not addessed with the pototype obots but ae being fully consideed in design of the next geneation. 3 Copyight 2002 by ASME

4 Cost pe obot is also citical in a decentalized appoach to obot safety makes. Multiple safety makes ae used in wok zones so costly makes ae not pactical. Also, baels ae often destoyed when stuck by passing vehicles. Safety makes with a high eplacement cost ae not pactical. Howeve, obots stuck by cas have pefomed thei function by indicating to the dive that the vehicle is not in the coect position. Mechanical and Mobility Design The obot mechanical design can be seen in Figue 2. The obot consists of a platfom that is simila to the base of a taditional safety bael. The obot has two 7 ½ in diamete wheels that ae independently diven by two motos. The ea of the obot has a passive caste. This kinematic aangement allows the obot to tun on any adius including tuning in place. The motos each have a high gea atio so the obot is not easily moved when the motos ae not poweed. This allows the obot to stay in place fo long peiods while using little o no powe. Since both the lead wheels ae poweed the obot can climb small bumps and obstacles. The bael snaps onto a ing aound the obot and encloses all components. The obot itself stands less than one foot tall and aises the bael height by thee inches. Figue 2: Robot Mechanical Design Electical Design The obot is poweed by a 12-volt lead acid battey (shown mounted above the caste in Figue 2). This application lends itself to sola echaging, howeve, this option was not consideed because of the desie to educe the pe obot cost. The bael obot has two pocessos-one is used fo obot contol and one to manage communication with the outside wold. Each obot has an RF tansceive that can tansmit and eceive infomation. Each moto has an encode that can be used to detect wheel position o speed. The obot is designed to pefom local contol (wheel speed and/o position) with highlevel planning being done eithe by the distibuted system of obots o by a emote planning system. This allows the obot pocessos to be simple, inexpensive, and edundant. CONTROL OF THE ROBOTIC SAFETY BARRELS The obotic safety baels can be opeated in many ways, anging fom being simply emotely diven (tele-opeation) to opeating autonomously. One mode of contol that has been implemented on the obot pototypes is emote diving. This simple appoach is advantageous because wokes can deploy safety makes fom a safe emote location. A joystick is used to dive the obot to its desied location. The base tansmitte sends out encoded commands that contain a obot identification numbe and two desied wheel speeds. Each obot is constantly listening fo commands. The opeato can change the obot identification numbe and dive all obots individually. Remote contol is simple and inceases woke safety by moving the opeato away fom dange. Howeve, it still equies woke time and obots ae deployed seially. An autonomous system would be pefeed. Autonomous contol is boken into two poblems- global planning and local contol. The poblem is divided in this manne to educe the pe obot cost. With this appoach each obot does not need to possess high computational ability. Also, this appoach equies only low-bandwidth communication with the cental contolle (o othe obots). Global Planning Motion planning fo mobile obots has been extensively studied. Seveal appoaches have been developed such as behavio contol [13], electostatic potential fields [14], pobabilistic maps [15], genetic planning [16] and othes. Pevious wok with multiple mobile obot contol fo highway maintenance has been done fo cack sealing obots [8, 17]. Hee, up to fou tetheed mobile obots wok togethe. This system uses a host compute as the cental intelligence and each obot becomes a wokstation in a Windows netwok. The obots can access and shae files but each emains independent. This is done to ceate a highly fault-toleant system. This appoach cannot be diectly applied to the safety bael obots because each obot will not have high computational ability. Also, the obots will not be tetheed making high bandwidth communication expensive. Othe eseach develops a hybid contol scheme fo fomations of non-holonomic mobile obots [18]. This method contols the motion of many obots while maintaining a pedetemined fomation. This wok also uses high bandwidth communication and complex vision sensos on each obot. The appoach being developed fo the obotic safety baels uses a single camea mounted on a maintenance vehicle. This 4 Copyight 2002 by ASME

5 camea would povide a view simila to the simulation image shown Figue 3. The video system identifies the location of each bael obot with espect to itself using the highway stipes as efeence. The contol system then tansmits a desied position to each obot. The obot itself moves to that position using its local contol system. Fo example in Figue 3, obot #4 must move 1 mete fowad and 1 mete to the left to join the fomation. The desied positions ae ceated based on a planning algoithm that dictates a seies of desied positions along a path. The path can be ceated in many ways, hee a polynomial is used. The bounday conditions fo this polynomial ae the beginning location and the desied end points and the initial deivative (the obot begins with locally fowad motion), see Figue 5. This appoach ensues the non-holnomic constaints ae consideed. The final oientation of the path is not constained so a new destination can be given while maintaining fluid motion. Figue 3: Contol Simulation The global contol scheme is cuently unde development in simulation. The local contolle, discussed in the following section is cuently being tested in a laboatoy setting. Othe eseach has studied the use of video to identify bael shaped objects [19] and the use of cameas fo obot contol in outdoo envionments [20]. Local Contol of Individual Robots Each bael obot will eceive a waypoint (i.e. desied position o desied velocity) fom the cental contolle. The obot will then use a local contol to obtain that position. A simple invese Jacobian Catesian scheme that uses PID contol has been implemented. This is a common appoach to obot contol whee an eo (δx) is ceated in Catesian space using a desied Catesian position (x d =[x d, y d, ψ d ]) and a measued position (x). This eo is tansfomed into joint space (δθ) using the invese jacobian. This eo is then acted upon by a taditional PID contol law to ceate left and ight toque commands (τ=[τ l, τ ]) fo the obot's motos. Contol of this type has seveal well known limitations (ignoes dynamic effects, non-holonomic constains) but initial tests have shown acceptable esults (5-10% position eo, e.g cm in a 1 mete motion) fo bael placement. Figue 5: Path Planning The contol scheme also equies a elationship between diffeential motion in Catesian space and diffeential motion in joint space. This jacobian elationship is nonlinea fo the obot safety baels. To find this diffeential elationship, conside the top view of the obot in Figue 6. Hee the obot has moved an amount δx=[δx, δy, δψ] between times t i-1 and t i. Duing this time the wheels have otated an amount δθ=[ δθ l, δθ ]. Figue 4: Invese Jacobian Catesian Contolle 5 Copyight 2002 by ASME

6 Figue 6 : Diffeential Robot Motion Duing this diffeential time the obot will tun about a given adius by an amount δψ, see Figue 7. position of the obot is detemined by accumulating diffeential motions, equation ( 4 ). X t t = X i t= t i 1 + δx = ( 4 ) This pocess (dead-eckoning) accumulates measuement eos. Laboatoy testing has shown this eo to be within 5-10% of the oveall motion. This eo accumulation is not citical since the global motion of the obot is detemined by the absolute extenal measuement of the video system used by the global planne. The contol scheme has been implanted and the esults ae shown in Figue 8. The obot was asked to tavel to a position [x=1 mete, y=1 mete] in thee seconds. The desied path is shown as a solid line and the actual path is shown with a dashed line. The obot aives at the desied position with 9.2% position eo. Figue 7: Tuning Radius Hee, S L and S R ae the paths of the left and ight wheels. No slip is assumed so the path lengths ae elated to the change in wheel angles by S=δθ whee is the wheel adius and δθ is given by the moto encodes. D is the distance between the wheels and R L and R R ae the tuning adii fo each wheel. If small motions ae assumed the diffeential motion in Catesian space can be found based on the diffeential motions in joint space. Using geomety, the elationships ae given by: δx = 2 δy = 2 [ δθ + δθ ] cos ( δθ δθ ) L R d [ δθ + δθ ] sin ( δθ δθ ) R L ( 1 ) ( 2 ) L R R L d δ Ψ = ( δθ R δθ L ) ( 3 ) d The position of the obot in Catesian space can only be detemined fom the changes in wheel position fo small motions of the obot. Fo lage motions the Catesian position of the obot is non-obsevable based on wheel angle. The Figue 8: Desied and Actual Robot Path FUTURE WORK Futue wok on the obotic safety baels will focus on inceasing the system's eliability, deceasing the pe obot cost, and the development of a global contol scheme fo a goup of obots. The thee pototypes cost appoximately $700 pe obot. Cost was not explicitly consideed in thei design and off-theshelf components wee used. Almost half the cost of the pototypes was spent on the two dive motos. It is estimated that the next geneation pototypes will cost aound half this amount. It is hoped that a mass poduction appoach can bing the cost pe obot to less than $200. The next geneation obots will also diectly conside fault toleance with tiple edundancy in evey citical system. Each obot will have seveal watchdog times that must be fequently 6 Copyight 2002 by ASME

7 eset o the system will be shut down. The cental contolle will boadcast a caie wave so that all obots can be stopped if a fault is detected. The obots may include thee independent pocessos that will vote on all commands. These and othe appoaches will be diectly incopoated into the next geneation design. Othe contol appoaches ae being investigated. Namely, a fully autonomous mobile obot is being pepaed to seve as the centalized contolle. This obot is much moe capable (lage computational ability, GPS, lase ange finde, steeo camea, etc) and will be a leade of seveal bael obots. This geneal/toops system has the potential fo moe autonomy. SUMMARY AND CONCLUSIONS This pape pesents a mobile obotic safety make system that uses mobile obots to tanspot safety makes fo highway constuction and maintenance. These obots wok in teams to povide taffic contol. Independent autonomous bael obots have seveal advantages. Fist, the baels can self-deploy-eliminating the dangeous task of manually placing baels in busy taffic. The bael positions can be quickly and emotely e-configued as the wok zone changes. Baels could continuously follow wok cews to maintain optimal placement. This pape descibed the motivation fo the obotic safety make system and how it could impove wok zone safety. The design of thee obot pototypes was descibed. A contol achitectue was biefly intoduced and a jacobian matix deived. The Robotic Safety Baels ae the fist elements of a team of Robotic Safety Makes (RSM) that includes signs, cones, and possibly baicades and aestos. Such devices ae not suitable fo evey wok zone, howeve thee ae many situations whee they would useful and pactical. ACKNOWLEDGMENTS This wok is sponsoed by the National Reseach Council Tanspotation Reseach Boad s NCHRP IDEA pogam. REFERENCES [1] Anon. The 11 Best Ways to Impove Wok Zone Safety. Bette Roads v60, n7 (1990): p [2] Ha, T.J., and Nemeth, Z.A. Detailed Study of Accident Expeience in Constuction and Maintenance Zones. Tanspotation Reseach Recod n1509 (1995): p [3] Ravani, B., and Velinsky, S.A. West, T.H. Requiements fo Application of Robotics and Automation in Highway Maintenance and Constuction Tasks. ASCE Specialty Confeence on Robotics fo Challenging Envionments (1994): p [4] Gumtau, Richad. Richad Gumtau on Taffic Contol and Wok Zones. Bette Roads v63, n9, [5] Shah, Shashikant. New Wok Zone Safety Devices. Poceedings of the ASCE 3 d Intenational Confeence on Applications of Advanced Technologies in Tanspotation Engineeing (1993): p [6] White, Thomas D. Evolving Automation in the Asphalt Paving Industy. TR News n176 (1995): p4-6. [7] West, Thomas H., and Velinsky, Steven A., and Ravani, Baham. Advanced Highway Maintenance and Constuction Technology Applications. TR News (1995): p [8] Lasky, Ty A., and Ravani, Baham. Senso-based Path Planning and Motion Contol fo a Robotic System fo Roadway Cack Sealing. IEEE Tansactions on Contol Systems Technology v8, n4 (2000): p [9] Woo, Dah-Cheng. Robotics in Highway Constuction and Maintenance. Public Roads v58, n3 (1995): p [10] Rihani, Rami A., and Benold, Leonhad E. Teleobotic Pavement Make Application. ASCE Confeence on Robotics fo Challenging Envionments (1996): p [11] Zhou, Tong, and West, Thomas. Assessment of the Stateof-the-At of Robotics Applications in Highway Constuction and Maintenance. Poc. of the 2 nd Intl. Conf. on Applications of Advanced technologies in Tanspotation Engineeing (1991): p [12] AHMCT website: ahmct.ucdavis.edu/ [13] Books, R., "A Robust Layeed Contol System fo a mobile obot," IEEE Tansactions on Robotics and Automation, Vol. 2, No. 1, [14] Khatib, O. "Real-time obstacle avoidance fo manipulatos and mobile obots," Intenational Jounal of Robotics Reseach, 5 (1), 90-98, [15] Boenstein, j., Koen, Y., "The Vecto Field Histogam- Fast Obstacle Avoidance fo Mobile Robots," IEEE Tans on Robotics and Automation, Vol. 7, No. 3 June [16] Faito S., Hacot H. and Dubowsky S., "Physics-Based Planning fo Planetay Exploation" IEEE Intl. Confeence on Robotic and Automation, [17] Feng, Xin, and Velinsky, Steven A. Development of a Distibuted Multiple Mobile Robot Contol System fo Automatic Highway Maintenance and Constuction. Midwest Symposium on Cicuits and Systems, Poceedings of the th Midwest Symposium on Cicuits and Systems v1 (1997). [18] Fieo R., Das A.K., Kuma V., Ostowski J.P., Hybid Contol of Fomations of Robots, IEEE Intl. Confeence on Robotic and Automation, [19] Hood, F. Hoff, W., King, R., "Evaluation of an Inteactive Technique fo Ceating Site Models fom Range Data", ANS Meeting on Robotics and Remote Systems, [20] Ollis, M., Stentz, A., "Vision-Based Peception fo an Autonomous Haveste" Poceedings of the IEEE/RSJ Intenational Confeence on Intelligent Robotic Systems, Vol. 3, 1997, pp Copyight 2002 by ASME