Latte art is a complex task requiring dexterity and precision, making it a challenging and commercially relevant task. A one-shot learning system is employed in which a single barista demonstration is segmented into five functionally distinct phases, each encoded as an independent Cartesian Dynamic Movement Primitive (CDMP) with its own parameters. Against a single-CDMP baseline, per-phase encoding reduces transition endpoint error by 3.2-4.5 times and art-stroke shape error by 2.7 times, reproducing jug tilt to below 1 degree RMS in the pouring phases. The learnt pour scales from a 280mL to a 400mL cup through a single spatial offset and a scaled recipe, with no re-demonstration. The phase-based CDMP approach generalises beyond latte art to any demonstration task whose phases have distinct spatial or temporal requirements whilst demonstrating the ability to adapt reproductions to suit different task requirements.
Figures & tables
Figure 1: Robot pour in motion with highlight results
#
Phase
Type
1
base_to_mix
transition
2
mixing
pouring
3
mix_to_art
transition
4
art
pouring
5
return_base
transition
Table 1: Phase decomposition of a latte art demonstration
Figure 2: Phase decomposition shown across each layer. Each column is one phase; rows show the human demonstration, the learnt primitives, and the robot reproduction.
280ml
400ml
Espresso dose
21g (single)
42g (double)
Milk volume
250ml
350ml
Rim diameter
80mm
90mm
Table 2: Beverage parameters for the two cup sizes.
Phase
αs
K
ρ
τ
base_to_mix
7.0
500
5.0
1.0
mixing
7.0
800
10.0
1.0
mix_to_art
7.0
700
6.0
4.0
art
7.0
800
8.0
1.0
return_base
7.0
500
5.0
1.0
Table 3: Per-phase CDMP parameters: temporal scaling τ , basis-function density ρ , stiffness K ( D=2K ).
Figure 3: Top-down trajectories of the mix_to_art transition for (a) the one-shot and (b) the phased reproduction, showing the human demonstration, the CDMP rollout and the executed robot motion.
Phase Evaluation Metric
Tilt RMS ( \SIUnitSymbolDegree )
Height RMS ( mm )
Phase
Type
Metric
E1
E2
×
Unit
E1
E2
E1
E2
base_to_mix
transition
endpoint error
30.1
9.5
3.2
mm
5.05
1.03
22.1
6.3
mix_to_art
transition
endpoint error
14.9
3.3
4.5
mm
9.51
0.61
60.8
18.7
return_base
transition
endpoint error
38.3
11.9
3.2
mm
9.35
3.54
40.7
12.4
mixing
pouring
coverage ratio
1.18
1.17
1.0
—
4.35
0.88
18.0
15.9
art
pouring
shape RMS
6.35
2.38
2.7
mm
3.15
0.75
11.3
16.5
Table 4: Per-phase comparison of one-shot (E1) and phased (E2) reproduction against the human demonstration. Phases are grouped by type. × denotes the improvement factor E1/E2; lower is better except for coverage ratio, where 1.00 is ideal.
Figure 4: Jug tilt relative to ground plane over the art phase for (a) the one-shot and (b) the phased reproduction.
Figure 5: Top-down photographs of the produced latte art. E1 is omitted as it was not poured with milk (Section 5.3 ).