problem connecting Irobot_create, Permission denied: '/dev/ttyACM0'?

edit

running the command on terminal

lsusb

it shows the serial to USB connectors connection as Sun Corp. (Suntac?):

Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
**Bus 003 Device 002: ID 05db:0012 Sun Corp. (Suntac?)**
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 003: ID 138a:003d Validity Sensors, Inc. 
Bus 001 Device 005: ID 04f2:b230 Chicony Electronics Co., Ltd Integrated HP HD Webcam
Bus 002 Device 003: ID 0a5c:21e1 Broadcom Corp.

running the command as bellow: I got to know it is connected at ttyACM0

dmesg | grep tty

But when running command on terminal

rosrun irobot_create_2_1 driver.py

the message appeared as"

could not open port /dev/ttyACM0: [Errno 13] Permission denied: '/dev/ttyACM0'