Robot-position detecting device and robot system

A robot system comprising:

• a position deciding unit including a first camera and an encoder that cooperate to decide a position of a work;
• a robot for moving the work;
• a second camera that takes an image of the work moved by the robot;
• a detection sensor that detects the work when the work is moved to a target position by the robot, the detection sensor including a light emitting unit that emits light toward a light receiving unit, and movement of the work is detected by the detection sensor when the movement of the work interrupts receipt of the light by the light receiving unit;
• and
• a controller that controls the robot,
• wherein the second camera is triggered to capture the image while the work is being moved, and
• wherein the robot includes:
• a position data acquiring unit, which is an encoder provided in the robot;
• a position calculating unit that receives a command for detecting a position of the robot and calculates the computational position of the robot;
• wherein first position data of the robot is data acquired at a timing earlier than the command;
• second position data of the robot is data acquired at a timing later than the command;
• and
• the position calculating unit includes a command detecting unit that detects the command at a period Ts shorter than a predetermined period T for acquiring the position data input to a position-data input unit from the encoder provided in the robot.