{"id":88,"date":"2018-09-21T10:44:05","date_gmt":"2018-09-21T10:44:05","guid":{"rendered":"http:\/\/www.stepperchina.com\/?p=88"},"modified":"2018-09-21T10:44:05","modified_gmt":"2018-09-21T10:44:05","slug":"open-loop-position-control-with-a-stepper-motor","status":"publish","type":"post","link":"https:\/\/www.stepperchina.com\/index.php\/2018\/09\/21\/open-loop-position-control-with-a-stepper-motor\/","title":{"rendered":"Open-loop Position Control with a Stepper Motor"},"content":{"rendered":"<p>With the increasing popularity of DIY projects such as quadcopters, CNC tables and 3D printers, many people are faced with the decision of which type of motor to use in their project. For applications that require precise control of the position of the motor, the common choices are <a href=\"https:\/\/en.wikipedia.org\/wiki\/DC_motor\">DC motors<\/a> with encoders, servo motors, and stepper motors.<\/p>\n<p>First, let\u2019s take a look at what the control system looks like on a <a href=\"https:\/\/www.oyostepper.com\/\">stepping motor for sale<\/a> without an encoder. Suppose you want the stepper to make one complete rotation. Your program knows your motor\u2019s step angle is (for example) 1.8\u00b0, so\u00a0it\u00a0tells your controller to move 200 steps clockwise. The controller tells this to the driver chip, and the driver chip outputs the power signals that turn the motor. Next, suppose you want the motor to turn half a rotation counter-clockwise from it\u2019s original starting location. Your program remembers\u00a0the motor is 200 steps away from the starting position, so it tells the controller to move 300 steps counter-clockwise, and so on.<\/p>\n<p><a href=\"https:\/\/phidgets.files.wordpress.com\/2014\/05\/openloop.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-515 size-large\" src=\"https:\/\/phidgets.files.wordpress.com\/2014\/05\/openloop.jpg?w=605&amp;h=85\" sizes=\"auto, (max-width: 605px) 100vw, 605px\" srcset=\"https:\/\/phidgets.files.wordpress.com\/2014\/05\/openloop.jpg?w=605&amp;h=85 605w, https:\/\/phidgets.files.wordpress.com\/2014\/05\/openloop.jpg?w=1210&amp;h=170 1210w, https:\/\/phidgets.files.wordpress.com\/2014\/05\/openloop.jpg?w=150&amp;h=21 150w, https:\/\/phidgets.files.wordpress.com\/2014\/05\/openloop.jpg?w=300&amp;h=42 300w, https:\/\/phidgets.files.wordpress.com\/2014\/05\/openloop.jpg?w=768&amp;h=108 768w, https:\/\/phidgets.files.wordpress.com\/2014\/05\/openloop.jpg?w=1024&amp;h=144 1024w\" alt=\"openloop\" width=\"605\" height=\"85\" data-attachment-id=\"515\" data-permalink=\"https:\/\/phidgets.wordpress.com\/2014\/05\/13\/steppers-with-encoders-when-open-loop-control-isnt-enough\/openloop\/\" data-orig-file=\"https:\/\/phidgets.files.wordpress.com\/2014\/05\/openloop.jpg\" data-orig-size=\"1500,211\" data-comments-opened=\"1\" data-image-meta=\"{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;}\" data-image-title=\"openloop\" data-image-description=\"\" data-medium-file=\"https:\/\/phidgets.files.wordpress.com\/2014\/05\/openloop.jpg?w=300\" data-large-file=\"https:\/\/phidgets.files.wordpress.com\/2014\/05\/openloop.jpg?w=605&amp;h=85\" \/><\/a><\/p>\n<p>This is known as open-loop control. You have precise control over the position of the motor, but only under the assumption that the motor has physically done exactly what it\u2019s been told to do. If the motor takes an extra step due to excessive inertia, if the motor stalls, or if you\u2019re using a <a href=\"https:\/\/www.oyostepper.com\/category-26-b0-Geared-Stepper-Motor.html\">gearbox stepper motor<\/a> that has significant backlash, your program\u2019s assumption of the motor\u2019s current state will be wrong.<\/p>\n<p><a href=\"https:\/\/blog.oyostepper.com\/2018\/09\/21\/closed-loop-position-control-with-a-dc-motor-and-encoder\/\">Closed-loop Position Control with a DC Motor and Encoder<\/a><\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>With the increasing popularity of DIY projects such as quadcopters, CNC tables and 3D printers, many people are faced with the decision of which type of motor to use in their project. For applications that require precise control of the position of the motor, the common choices are DC motors with encoders, servo motors, and &hellip; <a href=\"https:\/\/www.stepperchina.com\/index.php\/2018\/09\/21\/open-loop-position-control-with-a-stepper-motor\/\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;Open-loop Position Control with a Stepper Motor&#8221;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[],"tags":[],"class_list":["post-88","post","type-post","status-publish","format-standard","hentry"],"_links":{"self":[{"href":"https:\/\/www.stepperchina.com\/index.php\/wp-json\/wp\/v2\/posts\/88","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.stepperchina.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.stepperchina.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.stepperchina.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.stepperchina.com\/index.php\/wp-json\/wp\/v2\/comments?post=88"}],"version-history":[{"count":1,"href":"https:\/\/www.stepperchina.com\/index.php\/wp-json\/wp\/v2\/posts\/88\/revisions"}],"predecessor-version":[{"id":89,"href":"https:\/\/www.stepperchina.com\/index.php\/wp-json\/wp\/v2\/posts\/88\/revisions\/89"}],"wp:attachment":[{"href":"https:\/\/www.stepperchina.com\/index.php\/wp-json\/wp\/v2\/media?parent=88"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.stepperchina.com\/index.php\/wp-json\/wp\/v2\/categories?post=88"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.stepperchina.com\/index.php\/wp-json\/wp\/v2\/tags?post=88"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}