{"id":12,"date":"2024-04-04T08:01:21","date_gmt":"2024-04-04T05:01:21","guid":{"rendered":"https:\/\/sisu.ut.ee\/rosak\/pikem-soit\/"},"modified":"2024-04-04T08:03:59","modified_gmt":"2024-04-04T05:03:59","slug":"pikem-soit","status":"publish","type":"page","link":"https:\/\/sisu.ut.ee\/rosak\/pikem-soit\/","title":{"rendered":"8. Pikem s\u00f5it"},"content":{"rendered":"
\n

\n\t\tN\u00fc\u00fcd oskame robotit s\u00f5itma panna, kuid ainult l\u00fchikeseks ajaks. Mis siis, kui tahame, et ta s\u00f5idaks pikemat aega?<\/span><\/strong>\n\t<\/p>\n<\/blockquote>\n

\n\tSelleks, et roboti kasutamine oleks turvaline (n\u00e4iteks olukorras kus \u00fchendus roboti ja cmd_vel<\/span> kuulutaja vahel kaob), on roboti draiverisse sisse programmeeritud kaitsemehhanism, mis automaatselt peatab roboti mootorid, kui poole sekundi jooksul ei ole uut s\u00f5numit kiiruse infoga saabunud. Kui soovime, et robot liiguks edasi kauem kui pool sekundit, peame talle <\/span>pidevalt liikumisk\u00e4ske saatma<\/span>. Vaatame, kuidas oma koodi veidi muuta n\u00f5nda, et see liikumisk\u00e4ske regulaarselt kuulutaks.<\/span>\n<\/p>\n

#!\/usr\/bin\/env python3<\/span>\r\nimport rospy<\/span>\r\nfrom geometry_msgs.msg import Twist<\/span>\r\n\r\ndef main():<\/span>\r\n    rospy.init_node(\"velocity_publisher\")<\/span>\r\n    velocity_pub = rospy.Publisher(\"cmd_vel\", Twist, queue_size=0)\r\n    rospy.sleep(2)<\/span>\r\n\r\n    loop_rate = rospy.Rate(10)<\/span>\r\n    starting_time = rospy.get_time()<\/span>\r\n\r\n    while (not rospy.is_shutdown()) and (rospy.get_time() - starting_time < 5):<\/span>\r\n        robot_vel = Twist()<\/span>\r\n        robot_vel.linear.x = 0.1<\/span>\r\n        robot_vel.linear.y = 0.0<\/span>\r\n        robot_vel.linear.z = 0.0<\/span>\r\n        robot_vel.angular.x = 0.0<\/span>\r\n        robot_vel.angular.y = 0.0<\/span>\r\n        robot_vel.angular.z = 0.0<\/span>\r\n\r\n        velocity_pub.publish(robot_vel)<\/span>\r\n\r\n        loop_rate.sleep()<\/span>\r\n\r\nif __name__ == '__main__':<\/span>\r\n    try:<\/span>\r\n        main()<\/span>\r\n    except rospy.ROSInterruptException:<\/span>\r\n        pass<\/span><\/pre>\n
\n\t\u00a0\n<\/p>\n
\n\tAnal\u00fc\u00fcsime selle koodi t\u00f6\u00f6d.<\/span>\n<\/p>\n
starting_time = rospy.get_time()<\/span><\/pre>\n
\n\tSee rida paneb muutuja starting_time<\/span> v\u00e4\u00e4rtuseks praeguse kellaaja, m\u00f5\u00f5detuna sekundites kindlast ajahetkest minevikus. Teiste s\u00f5nadega: see \u00fctleb meile, kui mitu sekundit on m\u00f6\u00f6dunud teatud kindlast ajahetkest. Mis hetk see t\u00e4pselt on, see ei olegi meie jaoks oluline.<\/span>\n<\/p>\n
while (not rospy.is_shutdown()) and (rospy.get_time() - starting_time < 5):<\/span><\/span><\/pre>\n
\n\tSee rida tekitab ts\u00fckli, mis jookseb seni, kuni kehtivad kaks tingimust: ROSi t\u00f6\u00f6d pole peatatud (<\/span>not rospy.is_shutdown()<\/span>) ja vahe praeguse aja (rospy.get_time()<\/span>) ning koodi algusaja (starting_time<\/span>) vahel on v\u00e4iksem kui 5 sekundit. Tegelikkuses t\u00e4hendab see, et kood jookseb kuni 5 sekundit.<\/span>\n<\/p>\n
loop_rate = rospy.Rate(10)<\/span><\/pre>\n
\n\tning<\/span>\n<\/p>\n
loop_rate.sleep()<\/span><\/pre>\n
\n\tNeed read aitavad meil ts\u00fcklit k\u00e4imas hoida konstantse kiirusega. Robootikas on sageli kasulik, kui meie kood l\u00e4bib ts\u00fcklit kindla pikkusega. rospy.Rate(10)<\/span> tekitab meile v\u00f5imaluse panna koodi jooksma kiirusega 10 Hz (st 10 korda sekundis). Selle funktsiooni tagastatud v\u00e4\u00e4rtuse paneme muutujasse loop_rate<\/span>. Ning seej\u00e4rel saame ts\u00fckli l\u00f5pus v\u00e4lja kutsuda funktsiooni loop_rate.sleep()<\/span>, mis lihtsalt aeglustab ts\u00fckli l\u00e4bimist ja ootab, kuni ts\u00fckli l\u00e4bimiseks kulunud aeg on t\u00e4pselt k\u00fcmnendik sekundit.<\/span>\n<\/p>\n
\n
\n\t\tMiks programmi t\u00f6\u00f6d aeglustada?<\/span>
\n\t<\/h4>\n
\n\t\tProgrammi t\u00f6\u00f6 aeglustamine v\u00f5ib olla kasulik mitmes olukorras. Tavaliselt t\u00e4idab arvuti programmi nii kiiresti, kui v\u00f5imalik \u2013 kasutades selleks \u00e4ra k\u00f5ik oma ressursid. S\u00f5ltuvalt sellest, mida programm tegema peab, v\u00f5ib miljonite operatsioonide sooritamine \u00fches sekundis olla t\u00e4iesti ebapraktiline ning energiat raiskav. Selleks ongi programmeerimiskeeltes spetsiaalsed k\u00e4sud, millega programmi aeglustada. Need k\u00e4sud v\u00f5imaldavad anda vahepeal j\u00e4rg \u00fcle teistele programmidele ning aeglustada v\u00f5i teatud ajaks sootuks peatada protsessori t\u00f6\u00f6. Tasub t\u00e4hele panna, et isegi 0.01 sekundi pikkune paus, mis inimese jaoks tundub t\u00fchiselt v\u00e4ike v\u00f5ib olla arvuti jaoks terve igavik, sest protsessor suudab teha mitmeid tehteid \u00fches <\/span>nano<\/span>sekundis ehk 0.000000001 sekundis.<\/span>\n\t<\/p>\n
\n\t\tAeglustamist kasutatakse ka selleks, et programmi panna k\u00e4ima korduvalt t\u00e4pselt m\u00e4\u00e4ratud aja tagant.<\/span>\n\t<\/p>\n<\/blockquote>\n
\n\t\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"
N\u00fc\u00fcd oskame robotit s\u00f5itma panna, kuid ainult l\u00fchikeseks ajaks. Mis siis, kui tahame, et ta s\u00f5idaks pikemat aega? Selleks, et roboti kasutamine oleks turvaline (n\u00e4iteks olukorras kus \u00fchendus roboti ja cmd_vel kuulutaja vahel kaob), on roboti draiverisse sisse programmeeritud kaitsemehhanism, …<\/p>\n","protected":false},"author":98,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"class_list":["post-12","page","type-page","status-publish","hentry"],"acf":[],"_links":{"self":[{"href":"https:\/\/sisu.ut.ee\/rosak\/wp-json\/wp\/v2\/pages\/12","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sisu.ut.ee\/rosak\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/sisu.ut.ee\/rosak\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/sisu.ut.ee\/rosak\/wp-json\/wp\/v2\/users\/98"}],"replies":[{"embeddable":true,"href":"https:\/\/sisu.ut.ee\/rosak\/wp-json\/wp\/v2\/comments?post=12"}],"version-history":[{"count":1,"href":"https:\/\/sisu.ut.ee\/rosak\/wp-json\/wp\/v2\/pages\/12\/revisions"}],"predecessor-version":[{"id":389,"href":"https:\/\/sisu.ut.ee\/rosak\/wp-json\/wp\/v2\/pages\/12\/revisions\/389"}],"wp:attachment":[{"href":"https:\/\/sisu.ut.ee\/rosak\/wp-json\/wp\/v2\/media?parent=12"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}