Debian、Python3にてon() argument after * must be an iterable, not float　というエラー

実現したいこと

プログラムを正式に実行させ、mindstorms,EV3によるライントレースを成功させたい。

発生している問題・分からないこと

ライントレースを実行したいのだが、エラーが出てうまくいかない。

エラーメッセージ

error
1Traceback (most recent call last):
2  File "ex10_14.py", line 52, in <module>
3    follow_line()
4  File "ex10_14.py", line 40, in follow_line
5    tank_drive.on(*speed_left_turn)
6TypeError: on() argument after * must be an iterable, not float

該当のソースコード

Python3
1from time import sleep,time
2
3from ev3dev2.motor import MoveTank, OUTPUT_A, OUTPUT_C
4from ev3dev2.sensor.lego import ColorSensor, TouchSensor
5from ev3dev2.sound import Sound
6
7tank_drive = MoveTank(OUTPUT_A, OUTPUT_C)
8cs, ts = ColorSensor(), TouchSensor()
9snd = Sound()
10
11cs.mode = 'COL-REFLECT'
12
13WHITE,LIGHTGLAY,DARKGLAY,BLACK = 85, 65, 45, 25
14
15
16def follow_line(max_duration=0.25):
17
18    speed_forward = (20,20)
19    speed_left_turn, speed_right_turn = (0.15), (15,0)
20    speed_left_sharpturn, speed_right_sharpturn = (-5, 5), (5, -5)
21
22    time_on = time()
23
24    while time() - time_on < max_duration:
25
26        if ts.is_pressed:
27            break
28
29        intensity = cs.value()
30
31        if intensity > WHITE :
32            tank_drive.on(*speed_right_sharpturn)
33        elif intensity > LIGHTGLAY :
34            tank_drive.on(*speed_right_turn)
35        elif intensity > DARKGLAY :
36            tank_drive.on(*speed_forward)
37        elif intensity > BLACK :
38            tank_drive.on(*speed_left_turn)
39        else:
40           tank_drive.on(*speed_left_sharpturn)
41        if intensity > BLACK:
42            time_on = time()
43
44    tank_drive.off()
45    snd.beep()
46
47if __name__ == '__main__':
48    snd.speak('Ready.Puch the touch sensor to start.')
49    ts.wait_for_bump()
50    follow_line()
51