To find out the exact device run:
$ lsusb
To disable and enable the device(f.e. USB on port 2 and device ID 1):
1)Turn off device ID 2-1:
$ echo '2-1' |sudo tee /sys/bus/usb/drivers/usb/unbind
2)Turn device ID 2-1 back on:
$ echo '2-1' |sudo tee /sys/bus/usb/drivers/usb/bind
Alternatively, if you just want to reset a USB device, the bind/unbind can be tricky as the IDs can change overtime and you might accidently select another device.
In this case you could use the vendor and product IDs given by lsusb with usb_modeswitch.
F.e.: to identify a wireless adapter:
$ lsusb
Bus 001 Device 042: ID 7392:7811 Edimax Technology Co., Ltd EW-7811Un 802.11n Wireless Adapter [Realtek RTL8188CUS]
Bus 001 Device 035: ID 0409:005a NEC Corp. HighSpeed Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
You can reset the Wireless adapter from Edimax Technology by:
$ sudo usb_modeswitch -v 0x7392 -p 0x7811 --reset-usb